Extend check-function-bodies to allow label and directives

As PR target/116174 shown, we may need to verify labels and the directive
order.  Extend check-function-bodies to support matched output lines to
allow label and directives.

gcc/

	* doc/sourcebuild.texi (check-function-bodies): Add an optional
	argument for matched output lines.

gcc/testsuite/

	* gcc.target/i386/pr116174.c: Use check-function-bodies.
	* lib/scanasm.exp (parse_function_bodies): Append the line if
	$up_config(matched) matches the line.
	(check-function-bodies): Add an argument for matched.  Set
	up_config(matched) to $matched.  Append the expected line without
	$config(line_prefix) to function_regexp if it starts with ".L".

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>