c-typeck.c (lookup_field): If -fplan9-extensions, permit referring to a field using...

c-typeck.c (lookup_field): If -fplan9-extensions, permit referring to a field using a typedef name.

gcc/:
	* c-typeck.c (lookup_field): If -fplan9-extensions, permit
	referring to a field using a typedef name.
	(find_anonymous_field_with_type): New static function.
	(convert_to_anonymous_field): New static function.
	(convert_for_assignment): If -fplan9-extensions, permit converting
	pointer to struct to pointer to anonymous field.
	* c-decl.c (grokfield): If -fplan9-extensions, permit anonymous
	fields.
	(is_duplicate_field): New static function.
	(detect_field_duplicates_hash): If -fplan9-extensions, check for
	typedef names duplicating field names.
	(detect_field_duplicates): Likewise.
	* doc/invoke.texi (Option Summary): Mention -fplan9-extensions.
	(C Dialect Options): Document -fplan9-extensions.
	* doc/extend.texi (Unnamed Fields): Document -fplan9-extensions.
gcc/c-family/:
	* c.opt (-fplan9-extensions): New option.
gcc/testsuite/:
	* gcc.dg/anon-struct-11.c: New test.
	* gcc.dg/anon-struct-12.c: New test.
	* gcc.dg/anon-struct-13.c: New test.
	* gcc.dg/anon-struct-14.c: New test.

From-SVN: r164926