Removes trailing underscores from include guard
Moves the global table into _Table_locker

Makes globalsynctable a private static member of _Table_locker to limit
its visibility, and of course, get rid of a global.
Removes leading underscores.  standards, right?
Maps to mutex instead of mutex*
Removes original test to see if lock exists

Since the emplace will have to do the lookup anyway.  cuts the get_lock
function down to two logical lines.