Support -mxl-reorder and swap instructions.

Support -mxl-reorder and swap instructions.

	*  config/microblaze/microblaze.c:
	Check mcpu, pcmp requirement and set TARGET_REORDER to 0 if not met.
	*  config/microblaze/microblaze.h: Add -mxl-reorder to DRIVER_SELF_SPECS
	*  config/microblaze/microblaze.md: New bswapsi2 and bswaphi2
	instructions emitted if TARGET_REORDER
	*  config/microblaze/microblaze.opt: New option -mxl-reorder set to 1
	or 0 for -m/-mno case, but initialises as 2 to detect default use case
	separately

From-SVN: r196415