Accept --just-symbols symbols as absolute for xcoff

Accept --just-symbols symbols as absolute for xcoff

This patch is aimed at curing
    just-symbols-1.o: loader reloc in unrecognized section `*ABS*'
for xcoff by treating symbols defined by --just-symbols objects as
absolute.

	* xcofflink.c (xcoff_need_ldrel_p): Accept --just-symbols symbols and
	similar as absolute.
	(bfd_xcoff_import_symbol): Don't fuss over absolute symbol
	redefinitions here.