gas: handle csect in bss section for XCOFF

Latest gcc versions are now generating csects instead of .lcomm
for bss symbols.
Some adjustements are needed in order to handle them.

	* config/tc-ppc.c (md_begin): Create bss section with dummy
	symbol.
	(ppc_frob_symbol): Output XTY_CM for bss csects.
	(ppc_fix_adjustable): Adjust condition to avoid bss csects.
2 files changed