BCM2708:  Add enough infrastructrue (more stubs) to get a clean compilation of the Pi Zero configuration (with many undefined things at link time).

    BCM2708:  Add basic interrupt handling logic

    BCM2708: Add interrupt register definitions.

    BCM2708:  Add irq.h header file

    BCM2708/Pi zero:  bcm_boot.c and bcm_memorymap.h now compile.  Added pizero linker script.

    BCM2708/Pi Zero:  Add Make.defs needed to build.

    arch/arm/include/bcm2708, arch/arm/src/bcm2708, configs/pizero:  Add some basic build and configuration logic.

    configs/pizero:  Add some basic structure of the Rasperry Pi Zero port.

    Created directory configs/pizero.  Nothing there now but a README.txt file.

    Add initial boot.c and memorymap.c files
    Author: Alan Carvalho de Assis <acassis@gmail.com>

    Add AUX/UART/SPI registers definition
    Author: Alan Carvalho de Assis <acassis@gmail.com>

    Pizero GPIO registers
    * Initial commit to add GPIO definitions
    * Add remaining GPIO registers definition
    Alan Carvalho de Assis <acassis@gmail.com>

    BCM2708 memory map:  Add VBASE defintions; fix VCSDRAM address per Alan; move all virtual address to the bottom of the file to avoid confusion -- top is all physical address; bottom is all veritural address.

    Add initial memory map to BCM2708/BCM2835
    Alan Carvalho de Assis <acassis@gmail.com>

Master

* power: Add powerled to Kconfig

* stm32_powerled.c: cosmetics

* stm32_hrtim.c: cosmetics

* stm32/Kconfig: add HRTIM configuration and add DAC external trigger configuration

* stm32f334-disco: Add powerled example configuration

Approved-by: Gregory Nutt <gnutt@nuttx.org>

Stm32, stm32l4 serial patches

* stm32: serial: add interface to get uart_dev_t by USART number, stm32_serial_get_uart

* stm32: serial: do not stop processing input in SW flow-control mode

* stm32l4: serial: do not stop processing input in SW flow-control mode

* stm32l4: serial: suspend serial for Stop mode

Approved-by: Gregory Nutt <gnutt@nuttx.org>

    sched/mqueue:  Rename all private static functions for use the nxmq_ vs. mq_ naming.

    sched/mqueue:  Rename all OS internal functions declared in sched/mqueue/mqueue.h to begin with nxmq_ vs. mq_.  The mq_ prefix is reserved for standard application interfaces.

RNDIS: Use LPWORK for network operations by default

Master

* stm32_hrtim.c: fix burst mode prescaler update

* powerled.h: add fault field to state structure

* stm32f334-disco: add flash mode support for powerled driver + cosmetics

Approved-by: Gregory Nutt <gnutt@nuttx.org>

 libc and libnx:  When the libraries are built into two libraries, a user space library and a OS space library (as in the PROTECTED and KERNEL build).  Then the user space library must not use the OS internal interfaces; similarly, the OS must avoid using the userspace interfaces so that it does not muck the errno value or create spurious cancellation points.

libc and libnx:  When the libraries are built into two libraries, a user space library and a OS space library (as in the PROTECTED and KERNEL build).  Then the user space library must not use the OS internal interfaces; similarly, the OS must avoid using the userspace interfaces so that it does not muck the errno value or create spurious cancellation points.

configs/z80sim: Fix a naming problem.  Also, don't try to build the serial driver if CONFIG_NFILE_DESCRIPTOR=0.

libc/stdio:  Build the lib_noflush() and lib_snoflush() stubs even if CONFIG_FILE_DESCRIPTORS=0.  They may still be needed.

Fix some problems in the previous commits:  Forgot to update sigset() after change to prototype.  Also there was a stray semicolon in the change signal().

SDCC Fixes:  Change some prototypes and some assumptions about the size of unsigned int to get to a clean SDCC compile.

Fix some build problems after recent separation of internal OS from application interfaces.  The build problem only occurs in the PROTECTED and KERNEL builds where separate libraries are built for the applications and for use within the OS. In these cases, the correct interfaces must be used.  This commit fixes a few of these, so I can get through build testing, but there are many more that need fixin'.

sama5d4-ek:  Remove a really old defconfig example file that is so far out of date that it can only be misleading.

    Replace all calls to sigprocmask() in the OS proper with calls to nxsig_procmask().

    sched/signal:  Add internal OS interface nxsig_procmask().  This internal interface is equivalent to the standard sigprocmask() used by applications except that it does not modify the errno value.  Also fixes a problem in that the original sigprocmask() was not setting the errno.

    Replace all calls to sigqueue() in the OS proper with calls to nxsig_queue() to avoid accessing the errno variable.

    sched/signal:  Add nxsig_queue() which is functionally equivalent to sigqueue() except that it does not modify the errno variable.

    Replace all usage kill() in the OS proper with nxsig_kill().

    sched/signal:  Add nxsig_kill() which is functionally equivalent to kill() except that it does not modify the errno variable.

mm/: Heap semaphore logic needs to use nxsem_* interfaces when available, but the standard semaphores only when implementing a user-space heap.  Not this does introduce and issue:  the memory management functions them become cancellation points because of the use of sem_wait.

drivers/serial/tcdrain:  tcdrain() was recently added to the NuttX C library.  But there is a problem.  The specification of tcdrain() requires that it be a cancellation point.  In order to do this, tcdrain was moved from the C library into the OS and the addition cancellation point hooks were added.  In non-FLAT builds, access via system calls is also now supported.

Adds new OS internal functions nxsig_sleep() and nxsig_usleep.  These differ from the standard sleep() and usleep() in that (1) they don't cause cancellation points, and (2) don't set the errno variable (if applicable).  All calls to sleep() and usleep() changed to calls to nxsig_sleep() and nxsig_usleep().

Squashed commit of the following:

    Change all calls to usleep() in the OS proper to calls to nxsig_usleep()

    sched/signal:  Add a new OS internal function nxsig_usleep() that is functionally equivalent to usleep() but does not cause a cancellaption point and does not modify the errno variable.

    sched/signal:  Add a new OS internal function nxsig_sleep() that is functionally equivalent to sleep() but does not cause a cancellaption point.

  sigtimedwait() -> nxsig_timedwait()
  sigwaitinfo()  -> nxsig_waitinfo()
  nanosleep()    -> nxsig_nanosleep()

The internal OS versions differ from the standard application interfaces in that:

  - They do not create cancellation points, and
  - they do not modify the application's errno variable

Squashed commit of the following:

    sched/signal:  Replace all usage of sigwaitinfo(), sigtimedwait(), and nanosleep() with the OS internal counterparts nxsig_waitinfo(), nxsig_timedwait(), and nxsig_nanosleep().

    sched/signal:  Add nxsig_nanosleep().  This is an internal OS version of nanosleep().  It differs in that it does not set the errno varaiable and does not create a cancellation point.

    sched/signal:  Add nxsig_timedwait() and nxsig_waitinfo().  These are internal OS versions of sigtimedwait() and sigwaitinfo().  They differ in that they do not set the errno varaiable and they do not create cancellation points.