* c-common.c (c_common_attributes): Add gnu_inline attribyte.
	(handle_gnu_inline_attribute): New function.
	* c-decl.c (diagnose_mismatched_decls): Handle gnu_inline attribute.
	(merge_decls, start_decl, start_function): Likewise.
	* doc/extend.texi: Document gnu_inline attribute.

	* gcc.dg/inline-17.c: New test.

From-SVN: r118567