Guard less code with the JIT mutex

Guard less code with the JIT mutex

gcc/jit/ChangeLog:
	* jit-playback.c (gcc::jit::playback::context::compile): Acquire the
	mutex here, immediately before using toplev, and release it here, on
	each exit path after acquisition.
	(jit_mutex): Move this variable here, from jit-recording.c.
	(gcc::jit::playback::context::acquire_mutex): New function, based on
	code in jit-recording.c.
	(gcc::jit::playback::context::release_mutex): Likewise.
	* jit-playback.h (gcc::jit::playback::context::acquire_mutex): New
	function.
	(gcc::jit::playback::context::release_mutex): New function.
	* jit-recording.c (jit_mutex): Move this variable to jit-playback.c.
	(gcc::jit::recording::context::compile): Move mutex-handling from
	here into jit-playback.c's gcc::jit::playback::context::compile.
	* notes.txt: Update to show the new locations of ACQUIRE_MUTEX
	and RELEASE_MUTEX.

From-SVN: r218528