Port STM32F7 I2C driver to STM32L4

* arch/stm32l4: port STM32F7 I2C driver to STM32L4

    STM32L4 I2C driver is in work-in-progress state (plentiful of
    TODOs and #warnings) and lags many features found in more
    up-to-date STM32 I2C drivers. The peripheral on STM32F7 and
    STM32L4 are identical except for L4's 'wakeup from stop mode'
    flag and STM32F7's I2C driver is in more 'ready to use' state.

    Patch ports the STM32F7 I2C driver to STM32L4. The I2C clock
    configuration is kept the same as before (I2CCLK = PCLK1 80 Mhz)
    instead of switching to STM32F7 arch default that is I2CCLK=HSI.
    Further work would be to add configuration option for choosing
    I2C clock source instead of current hard-coded default.

* arch/arm/stm32f7: i2c: restore bus frequency after I2C reset

    Copy frequency restoration fix from STM32L4 I2C driver to STM32F7 I2C driver.

* arch/arm/stm32f7: i2c: remove unused Kconfig option

* configs/nucleo-l496zg/nsh: enable I2C4 bus with i2ctool

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

Olimex stm32-h407 serial support for the on-board UEXT connector (fixed style & defconfig)

* olimex-stm32-h407: Add USART6 for UEXT connector.

* olimex-stm32-h407: nsh_uext configuration and README update.

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

sched: move POSIX thread specific data from pthread TCB to common TCB structure.  This change allows using pthread_getspecific/pthread_setspecific from main thread. Patch also enables using pthread data with config option CONFIG_DISABLE_PTHREAD=y.

mm/mm-heap: memalign: fix heap corruption caused by using unaligned chuck size.  Unaligned nodes generated by memalign later cause heap corruptions when nodes are shrink further (for example, 24 bytes -> 8 bytes, when alignment is 16 bytes).

This commit adds support for semi-standard IPPROTO_ICMP6 sockets.  This is a replacement for the non-standard ICMPv6 ping support that violated the portable POSIX OS interface.

Squashed commit of the following:

    net/icmpv6: IPPROT_ICMP6 socket logic now builds without error.
    net/icmpv6:  Add support for read-ahead and poll(). Initial commit is just cloned from ICMP with the appropriate name changes.
    configs/:  All defconfig filess that include CONFIG_NET_ICMPv6_SOCKET=y need to select CONFIG_SYSTEM_PING6=y and deselect CONFIG_DISABLE_POLL.
    Update NSH documention to show that ping6 is now a built in command.
    net/icmpv6:  Add icmpv6_sendto.c and icmpv6_recvfrom.c.  Initial versions are just clones from icmp/ with appropriate name changes.
    net/icmpv6:  Clone some ICMP socket logic as the beginning of support for ICMPv6 socket support.
    Rename CONFIG_NET_ICMPv6_PING to CONFIG_NET_ICMPv6_SOCKET.  Move prototype for icmpv6_ping from include/nuttx/net/icmpv6 to net/icmpv6/icmpv6.h

This change adds support for semi-standard IPPROTO_ICMP AF_INET datagram sockets.  This replaces the old ad hoc, nonstandard way of implementing ping with a more standard, socket interface.

Squashed commit of the following:

    net/icmp:  Finishes off icmp_recvfrom().
    net/icmp:  Add readahead support for IPPROTO_ICMP sockets.
    net/icmp:  Add poll() support for IPPROTO_ICMP sockets.
    net/icmp:  Add a connection structure for IPPROTO_ICMP sockets.
    net/icmp:  Implements sendto for the IPPROTO_ICMP socket.
    net/icmp:  Move icmp_sendto() and icmp_recvfrom() to separate files.  They are likely to be complex (when they are implemented).
    net/icmp:  Hook IPPROTO_ICMP sockets into network.  Fix some naming collisions.  Still missing basic ICMP send/receive logic.
    configs: apps/system/ping current need poll() enabled.
    configs: All defconfig files that use to enable low-level support must now enabled CONFIG_SYSTEM_PING.
    net/icmp:  Adds basic build framework to support IPPROTO_ICMP sockets.

stm32f103-minimum:  Add an ADPS-9960 example configuration

Master

* stm32_hrtim: fix warnings related with RCC

* stm32f33xxx_adc: add some publicly visable interfaces and some code to support injected channels

* stm32f33xxx_dma: add public interface to handle with DMA interrupts

* stm32_hrtim: change some names and add some coments

* chip/stm32f33xxx_adc.h: cosmetics

* nucleo-f334r8: add logic for zero latency high priority interrupts example

* stm32: update some ADC-related configuration in Kconfig

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

    fs/fat:  Remove mkfatfs from the OS.  This is a user-space application and belongs in apps, not in the OS.

drivers/bch:  The character driver to block device access now supports an IOCTL to get the geomtry of the underlying block device.

stm32_adc.c: clear pending interrupts

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

STM32L1, STM32L4 RTC: add periodic interrupts, update L1 RTC implementation

* STM32L4 RTC: add support experimental CONFIG_RTC_PERIODIC

* STM32 RTC: separate STM32L1 RTC into a separate file

    STM32L1 RTC is very close to F4 or L4 versions, with two alarms
    and periodic wakeup support so backported L4 peripheral to L1.

* RTC: add periodic alarms to upper and lower halves

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

net/tcp:  Same change to tcp_send_buffered.c probably also applies to sixlowpan_tcpsend.c and inet_recvfrom.c

Master

* stm32f33xxx_adc.c: fix some warnings and compilation error when extsel not in use

* nucleo-f334r8/adc: change serial console to USART2 (STLINK COM)

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

There was a possible recursion that could eventually overflow the stack.  The error occurred when closing the socket with inet_close() while a socket callback was still queued.  When the socket callback was executed by devif_conn_event(), this resulted in a call to psock_send_eventhandler() with TCP_CLOSE flag set which then called tcp_lost_connection().  tcp_shutdown_monitor() then called tcp_callback() again, which again called psock_send_eventhandler(), and so on....  Noted by Pascal Speck.  Solution is also similar to a solution proposed by Pascal Speck.

There was a reference counting problem in the TPC logic of net_clone().  net_clone() which is the common logic underlying dup() and dup2() for sockets.  When net_clone() calls net_start_monitor() and net_start_monitor() returns a failure (because the underlying TCP connection) then net_clone() must back out the reference count on the structure.  Problem noted by Pascal Speck and this implementation of the solution is based on his suggestion.