* threads.c (key_lock): Change to a k5_mutex_t.

* threads.c (key_lock): Change to a k5_mutex_t.
(k5_key_register): Use k5_ lock routines.
(pthread_getspecific, pthread_setspecific, pthread_key_create,
pthread_key_delete) [HAVE_PRAGMA_WEAK_REF]: Declare weak.
(tsd_if_single) [HAVE_PRAGMA_WEAK_REF]: New variable.
(krb5int_thread_support_init): Do pthread key creation only if pthread code is
loaded.
(krb5int_thread_support_fini): Do pthread key deletion only if pthread code is
loaded.
(k5_key_register, k5_getspecific, k5_setspecific): Use tsd_if_single when
pthread code is not loaded.

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@16502 dc483132-0cff-0310-8789-dd5450dbe970