build: move HAVE_POSIX_RWLOCK to exported config

This is b ecause we use this flag to decide whether the rwlock is implemented
from posix or whether we use our own structure. That influences the size and
offsets in cl_core. Without this commit using

(defun known-signals ()
  (ffi:c-inline nil nil :object "cl_core.known_signals"
                        :one-liner t :side-effects nil))

While HAVE_POSIX_RWLOCK was true during the build returns garbage. The same
applies to other members after the processes group.

src/h/config-internal.h.in

@@ -131,8 +131,6 @@
 #undef HAVE_SCHED_YIELD
 /* whether we have a working sem_init()                                 */
 #undef HAVE_SEM_INIT
-/* whether we have read/write locks                                     */
-#undef HAVE_POSIX_RWLOCK
 /* whether we have mutex lock operations with timeout                   */
 #undef HAVE_PTHREAD_MUTEX_TIMEDLOCK
 /* whether we can set the clock for timed waits on condition variables  */

src/h/config.h.in

@@ -235,6 +235,9 @@ typedef unsigned char ecl_base_char;
 /* wide-strings are available */
 #undef HAVE_WCHAR_H
 
+/* whether we have read/write locks                                     */
+#undef HAVE_POSIX_RWLOCK
+
 /*
  * C macros for inlining, denoting probable code paths and other stuff
  * that makes better code. Most of it is GCC specific.