coff make_a_section_from_file tidy

Also support compressing a few more sections.

	* coffgen.c (make_a_section_from_file): Rename return_section
	to newsect.  Don't try to be clever matching section name.
	Compress .gnu.debuglto_.debug_ and .gnu.linkonce.wi. too.
	Only rename debug sections when decompressing for linker.