Fix error in AT91SAM SPI driver introduced in recent comment.  Varioius improvements to README files and debug output

Add support for a generic windows-based EABI toolchain; Add NX configuration to force default NXTK border colors

Correct border colors for SAM3U-EK border; clean up some comments; make sure that sam_vectors.S is identical to stam32_vectors.S

Remove CONFIG_XYZ_BUILTIN configurations, replace with the single CONFIG_NSH_BUILTIN_APPS.  Add SAM3/4 sam_periphclks.h which is just a header file that includes the right header file.  Misc SAM3U-EK cleanup

Beginning updates of SAM3U header files o include support for the SAM4S: WDT, SUPC, EEFC, MATRIX, and PMC