pthread-rwlock: Fix default wait queue behaviour on glibc/Linux.
* lib/pthread.in.h: If REPLACE_PTHREAD_RWLOCK_INIT is 1 but
REPLACE_PTHREAD_RWLOCK_DESTROY is 0, override
PTHREAD_RWLOCK_INITIALIZER.
* lib/pthread-rwlock.c
(pthread_rwlockattr_init) [PTHREAD_RWLOCK_BAD_WAITQUEUE]: New function.
(pthread_rwlock_init) [PTHREAD_RWLOCK_BAD_WAITQUEUE]: New function.
* m4/pthread-rwlock.m4 (gl_PTHREAD_RWLOCK): Check for reasonable
pthread_rwlock wait queue handling. Set REPLACE_PTHREAD_RWLOCK_INIT and
REPLACE_PTHREAD_RWLOCKATTR_INIT and define PTHREAD_RWLOCK_BAD_WAITQUEUE
if not.
* modules/pthread-rwlock (configure.ac): Update
GL_COND_OBJ_PTHREAD_RWLOCK condition.