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

All minnsh configurations: Removing CONFIG_ARCH_STACKDUMP we reduce more 424 bytes.  Alan Carvalho de Assis

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

LPCXpresso-LPC1115:  Add a minimal NSH configuration that has the file system disabled.  Update README with OpenOCD instructions.  From Alan Carvalho de Assis.

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