* generic/vfs.c: move static globals to being thread-specific. If

	* generic/vfs.c: move static globals to being thread-specific.  If
	you wish to access a mount point or volume in a thread, you need
	to remount the file in the thread.  This is a change from the
	previous behavior that would allow access across threads, which
	was unsafe and would potentially crash.
		**** POTENTIAL INCOMPATIBILITY ****