Moved the implementation of the pthread wrappers to dlls/kernel.

diff --git a/configure.ac b/configure.ac
index 7fee56e..05a06df 100644
--- a/configure.ac
+++ b/configure.ac
@@ -520,6 +520,10 @@
     AC_DEFINE(HAVE___VA_COPY, 1, [Define if we have __va_copy])
 fi
 
+dnl **** Check for pthread_rwlock_t ****
+AC_CHECK_TYPES([pthread_rwlock_t, pthread_rwlockattr_t],,,[#define _GNU_SOURCE
+#include <pthread.h>])
+
 dnl **** Check for Open Sound System ****
 AC_CHECK_HEADERS(sys/soundcard.h machine/soundcard.h soundcard.h, break)