user_mutex: Per-team contexts.

This requires the introduction of the flag B_USER_MUTEX_SHARED, and then
actually using the SHARED flags in pthread structures to determine when
it should be passed through.

This commit still uses wired memory even for per-team contexts.
That will change in the next commit.

GLTeapot FPS seems about the same.

Change-Id: I749a00dcea1531e113a65299b6d6610f57511fcc
Reviewed-on: https://review.haiku-os.org/c/haiku/+/6602
Reviewed-by: waddlesplash <[email protected]>
Tested-by: Commit checker robot <[email protected]>

headers/private/libroot/pthread_private.h

@@ -19,6 +19,9 @@
 #define THREAD_CANCEL_ENABLED		0x08
 #define THREAD_CANCEL_ASYNCHRONOUS	0x10
 
+// _pthread_mutex::flags values
+#define MUTEX_FLAG_SHARED	0x80000000
+
 
 struct thread_creation_attributes;