arch/arm/src/lpc17xx:  Add support for ARMv7-M run time stack checking on NXP LPC17xx MCUs based on CONFIG_ARMV7M_STACKCHECK. Basically copied from stm32.

configs/freedom-k28f:  If drivers/leds/rgbled.c is enabled, then treat the board as though it had no discrete LEDs.

drivers/leds/rgbled.c:  Fix a compilation error introduced with a recent change to add multi-channel operation to RGB LED driver.

configs/freedom-k28f:  With these changes to the configuration, the NSH configuration is now functional on the k28f board.  Also fixes corrects the active logic level for the RGB LED.   arch/arm/src/kinetis/chip:  Fixes an error in vector configuration.

arch/arm/src/nrf52/nrf52_flash.c:  Add missing erasesize method.  Add missing function header comments.

libc/libc.csv: Fix missing or duplicate quotation marks.  mksymtab was not able to parse libc/libc.csv due to missing or duplicate quotation marks.

    configs/freedom-k28f:  Add button and LED support.
    arch/arm/src/kinetis:  Fix a couple of additional compile problems.
    arch/arm/src/kinetis/chip and configs/freedom-k28f:  Add things needed for a successful build.  Still need board LED definitions.

     arch/arm/src/kinetis:  The K28F Kinetis MPU is almost the same as the K66F MPU.
     arch/arm/src/kinetis:  The K28F Kinetis FMC is the same as the K66F FMC.

configs/photon: Adds RGB led support

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

drivers/sensors: Adds support for INA3221 power sensor. This has a 3 channel bus/shunt voltage pairs.

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

drivers/rgbled: Adds support for multichannel PWM (multiple PWM channels on a single timer)

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

fs/nfs/rpc_clnt.c:  Commit 091e3f73 broke the NFS client.  sendto() can (correctly) no lnoger by used with a connected UDP socket.  In that case, send() must be used instead.

This commits adds initial support for the Kinetis Freedom-K28F board.  Not you ready for prime time.

Squashed commit of the following:

    arch/arm/src/kinetis:  A fixes from first (unsuccessful) attempt to build the Freedom-K28F configuration.
    configs/freedom-k28f:  Add basic board support for Freedom-K28F.  Initial commit is basically just the Teensy-3.x brought up to date and with name changes.

arch/arm/src/lpc17xx: This commit adds a configurable option to allow using a part of LPC17xx's internal flash memory as a Memory Technology Device via NuttX' mtd_progmem infrastructure. Tested with LPC1769.

configs/imxrt1050-evk:  This commit adds support for the imxrt button.  I haven't been able to get GPIO 5 to work so I have replaced the button with GPIO1 pin24. It is right next to the button so I just wire it to the existing user button for testing.

  imxrt_gpioirq.c
    - Add check for interrupt mask register before dispatching ISR. The GPIO_ISR bits are set independent of the GPIO_IMR bits.
  imxrt_irq.c
    - fixed a range check for extint in function imxrt_irqinfo().

Squashed commit of the following:

    arch/arm/src/kinetis:  Add K28F memory map.
    arch/arm/src/include/kinetis and src/kinetis:  Add basic chip features and interrupt-related definitions for the K28F

configs/nrf52-pca10040:  Fix an error in the name of an included file.  This was introduced with the previous change to this file.

progmem interface: Discern r/w and erase page sizes.  Introduce new up_progmem_erasesize architecture API to be able to communicate the read/write page size independently from erase page size.  Implement up_progmem_erasesize for all architectures that already support progmem, assuming that for those architectures the sizes of both read/write and erase pages are identical.

arch/arm/src/nrf52:  Fix several inconsistencies in naming.  Mostly cosmetic but one was causing a compiler warning.