libgomp: Use pthread mutexes in the nvptx plugin.

libgomp: Use pthread mutexes in the nvptx plugin.

... instead of libgomp's internal mutex implementation.  Plugins aren't to
depend on internal libgomp interfaces, and how would you instantiate a
gomp_mutex_t in a plugin without knowing what it is exactly?

	libgomp/
	* plugin/plugin-nvptx.c (struct ptx_device): Turn stream_lock
	member into a pthread_mutex_t.  Adjust all users.
	(ptx_event_lock): Likewise.
	* libgomp-plugin.c (GOMP_PLUGIN_mutex_init)
	(GOMP_PLUGIN_mutex_destroy, GOMP_PLUGIN_mutex_lock)
	(GOMP_PLUGIN_mutex_unlock): Remove.
	* libgomp-plugin.h (GOMP_PLUGIN_mutex_init)
	(GOMP_PLUGIN_mutex_destroy, GOMP_PLUGIN_mutex_lock)
	(GOMP_PLUGIN_mutex_unlock): Likewise.
	* libgomp.map (GOMP_PLUGIN_1.0): Remove GOMP_PLUGIN_mutex_init,
	GOMP_PLUGIN_mutex_destroy, GOMP_PLUGIN_mutex_lock,
	GOMP_PLUGIN_mutex_unlock.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gomp-4_0-branch@219467 138bc75d-0d04-0410-961f-82ee72b054a4