remove DebugLoc from MCInst and eliminate "Comment printing" from

the MCInst path of the asmprinter.  Instead, pull comment printing
out of the autogenerated asmprinter into each target that uses the
autogenerated asmprinter.  This causes code duplication into each
target, but in a way that will be easier to clean up later when more
asmprinter stuff is commonized into the base AsmPrinter class.

This also fixes an xcore strangeness where it inserted two tabs
before every instruction.

llvm-svn: 81396