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.

drivrs/mtd/filemtd.c: add block device MTD interface.  Block MTD interface allows using block device directly as MTD instead of having to use file-system in between.  NOTE that this provides the opposite capability of FTL which will let you use an MTD interface directly as a block device.

drivers/ioexpander:  The IRQ subsystem now supports passing a void * parameter to IRQ handlers.  Use that method to support multiple pc9555 devices, by passing a pointer to the device to the board defined irq handler.  Now the CONFIG_ for multiple PCA devices just allocates device structures dynamically instead of statically when not enabled.

The same interrupt handler is entered with the device structure parameter in all situations,
multiple or single PCA. One should still be careful if multiple PCA devices share the same IRQ.

The timer frequencies (BOARD_TIMx_FREQUENCY) are incorrectly defined in configs/stm3240g-eval/include/board.h.  Since the APB prescalers are set to divide by 4 and 2 respectively, the frequencies should be "2xAPBx" as said in the comment.  The correct frequencies are already defined but as STM32_APBx_TIMx_CLKIN.

Lower part of STM32 CAN driver arch/arm/src/stm32/stm32_can.c uses all three hw tx mailboxes and clears TXFP bit in the CAN_MCR register (it means transmission order is defined by identifier and mailbox number).

This creates situation when order frames are put in upper part of CAN driver (via can_write) and order frames are sent on bus can be different (and I experience this in wild).

Since CAN driver API pretends to be "file like" I expect data to be read from fd the same order it is written. So I consider described behaviour to be a bug.

I propose either to set TXFP bit in the CAN_MCR register (FIFO transmit order) or to use only one mailbox.

BCM2708:  The PiZero configuration now compiles and links cleanly.  Still a few thngs missing internally.

photon: Support SPI1 and SPI3

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

drivers/usbdev:  Move test for NULL pointer before the pointer is deferences.  Noted by Juha Niskanen.

fs/vfs:  Fix after recent changes.  write() was return negative values in errno. Noted by Jussi Kivilinna.

drivers/usbdev: Correct input flow control logic when watermarks are not enabled.  Problem not by and change based on suggestion by Juha Niskanen.