SAMA5: The ostest configuration have been converted to run out of NOR flash.  There is more to be done, however

Fix an uninitialized register error that crept into the ARM9 start up code many years ago and was recently cloned into the Cortex-A5.  Obviously no on has used NuttX with ARM9 for years

Revamp the way external memory regions are configured; Add logic to add SAMA5 external memory regions to the heap

Improve some ARMv7-A/M floating point register save time; Add floating point register save logic for ARMv7-A

ARMv7-A:  Need 8-byte stack alignment when callign C code from interrupt handlers.  This change needs to be ported to other ARM architectures as well

SAMA5 clock configuration should now agree with Atmel sample code; Added header file with macros to enable and disable peripheral clocking

SAMA5/Cortex-A: Improve irqsave/restore inlines + add irqenable.  Add skeleton file for SAMA5 interrupt management.  Also change from last commit that was left in the editor