Add a bare bones framework that will do nothing more than support configuration for the Atmel SAMV71 Xplained Ultra board.  Very much a work in progress.

Rename all use of up_boardinitialize().  Should not use common microprocessing naming convention but rather the microprocessor-specific naming conventioni

configs/: board function prototypes are now in include/nuttx/board.h.  Remove from board header file; Add inclusion of nuttx/board.h to all files referencing board functions

PIC32MZ: Make sure that the microMIPS ISA is selected on all common MIPS32 assembly files when the PIC21MZ is selected

MIPS:  Add some build support for the M14K and also for the PIC32MZ Starter Kit.  Still a long way to go