Clean up some kernel build heap allocation issues.  The Cortex-A kernel build now compiles without errors (but cannot link until brk() and sbrk() are implemented).

SAMA5D4-EK:  Add a configuration for testing the kernel build configuration (still a work in progress)

Separate flat, protected, and kernel mode library selected into separate files.  The conditional logic as exceed my able to comprehend and maintain the selections.

Various changes/fixes to get configs/stm32f4discovery/kostest working after the big configuration renaming (and after a long period of bit rot)