We really need to include the header for the test to be reliable

svn path=/trunk/m4/; revision=4537

m4/acx_pthread.m4

@@ -164,7 +164,7 @@ if test "x$acx_pthread_ok" = xyes; then
         if test "x$flag" != xno; then
                 PTHREAD_CFLAGS="$flag $PTHREAD_CFLAGS"
         fi
-        AC_CHECK_TYPES(pthread_rwlock_t)
+        AC_CHECK_TYPES(pthread_rwlock_t,,,[#include <pthread.h>])
 
         LIBS="$save_LIBS"
         CFLAGS="$save_CFLAGS"