* struc-symbol.h (struct symbol): Add sy_mri_common bit.

	* struc-symbol.h (struct symbol): Add sy_mri_common bit.
	* read.h (mri_comon_symbol): Declare.
	(s_mri_common): Declare.
	* read.c (mri_line_label): New static variable.
	(mri_common_symbol): New global variable.
	(potable): Add "common" and "common.s".
	(read_a_source_file): In MRI mode, set mri_line_label for a label
	at the start of a line.
	(s_mri_common): New function.
	(s_space): Handle mri_common_symbol.
	* symbols.c (colon): Change return value from void to symbolS *,
	and return new symbol.  If mri_common_symbol is set, attach the
	new symbol to it.
	(resolve_symbol_value): Handle an sy_mri_common symbol.
	* symbols.h (colon): Change return value in declaration.
	* subsegs.c (subseg_set_rest): Clear mri_common_symbol.
	(subseg_set (both versions)): Likewise.
	* frags.c (frag_more): Warn if mri_common_symbol is not NULL.
	* write.c (adjust_reloc_syms): Skip sy_mri_common symbols.
	(write_object_file): Discard sy_mri_common symbols.
	(fixup_segment): Change relocations against sy_mri_common symbols
	to be against the common symbol itself.
	* config/obj-coff.c (yank_symbols): Discard sy_mri_common symbols.
	(fixup_segment): Change relocations against sy_mri_common symbols
	to be against the common symbol itself.
	* config/obj-aout.c (obj_crawl_symbol_chain): Discard
	sy_mri_common symbols.