decl2.c (comdat_linkage): Also set DECL_COMDAT.

	* decl2.c (comdat_linkage): Also set DECL_COMDAT.
	(finish_file): Check DECL_COMDAT instead of weak|one_only.
	(import_export_vtable): Use make_decl_one_only instead of
 	comdat_linkage for win32 tweak.
	(import_export_decl): Likewise.
	* pt.c (mark_decl_instantiated): Likewise.

Fix libgcc with -O3.

From-SVN: r17056