Update mutex debug code to be somewhat compatible with multi-threaded

Update mutex debug code to be somewhat compatible with multi-threaded
execution.  It won't be as useful in single-threaded programs for detecting
bugs in the mutex handling for now, though.

* k5-thread.h (k5_mutex_debug_check_init, k5_mutex_debug_update_loc): New
macros.
(k5_mutex_debug_lock, k5_mutex_debug_unlock): Use them.
(k5_mutex_lock, k5_mutex_unlock) [ENABLE_THREADS && DEBUG_THREADS]: Use them
instead of k5_mutex_debug_lock and k5_mutex_debug_unlock.
(enum k5_mutex_debug_states): New enum.
(K5_MUTEX_DEBUG_LOCKED, K5_MUTEX_DEBUG_UNLOCKED): Change to enumerator values.
(k5_mutex_debug_info): Use the enum type.  Reorder fields.
(K5_MUTEX_DEBUG_INITIALIZER): Update for new field order.

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@16293 dc483132-0cff-0310-8789-dd5450dbe970