Basic support for the Kinetis K20 architecture.  Taken from PX4.  This is the work of Jakob Odersky.

SAML21-Xlplained: Add options to enable XOSC32K and to use it as the DFLL source; NSH configure now uses DFLL with OSC16M source

Logic that samples the free running counter reads the pending interrupt status regsiter and can cause interrupts to be lost.  So, if when the status regsiter is read, the logic must also handle the timer overflow event.  Found and fixed by Max Neklyudov

LPC11xx: Use offsets instead of absolute address in look-up tables.  This saves about 156 bytes of FLASH.  From Alan Carvalho de Assis.

SAM4L:  Re-order some clock initialization.  There was a dependency of GCLK0 on DFLL, but DFLL was being enabled after GCLK0

LPC11xx: Add support for up_getc() which is needed for NSH if there is no file system.  From Alan Carvalho de Assis.

SAMD/L: Change ordering of some initialization steps to match Atmel sample code.  Add Errate 13134 support.  SAML wait states changed to 1.  Sample code is using 0

Initial support for the NXP LPC11 family and the LPC1115 MCU in particular.  Contributed by Alan Carvalho de Assis.

SAML21 clock config: Fix a misthink in last commit.  Move setting of ONDEMAND to after clock is enabled in most cases

SAML21: Add logic to support GLCK peripheral channels; add logic to configure FDPLL lock timer and ref clock GCLKs

STM32: Building stm32_rng.c should be conditioned on CONFIG_STM32_RNG, not CONFIG_DEV_RANDOM.  From Juha Niskanen

SAM3/4 Serial:  In NONBLOCKING mode serial does not receive bytes from UART.  This happens because RX interrupt was disabled in the setup routine.  To fix this I save interrupt configuration before uart shutdown and restore it after.  From Max Neklyudov.

SAML21-Xplained:  Update the cloned SAMD20-Xplained board configuration for specifics of the SAML21-Xplained

SAMD/L: Hide differences in the way peripheral clocking is enabled behind macros.  Some updates to saml_clockconfig.h + various fixes while working toward SAML21 build

Clock configuration logic for the SAML21.  Initial commit is just the SAMD20 clock configuration with some naming changes and does not compile