Replaced test for FILE::_lock by a more direct test.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@8670 a5019735-40e9-0310-863c-91ae7b9d1cf9
diff --git a/drd/drd_pthread_intercepts.c b/drd/drd_pthread_intercepts.c
index da4e552..e16845d 100644
--- a/drd/drd_pthread_intercepts.c
+++ b/drd/drd_pthread_intercepts.c
@@ -103,7 +103,7 @@
   /* more than one thread. Suppress data race reports on these objects.    */
   DRD_IGNORE_VAR(*stdout);
   DRD_IGNORE_VAR(*stderr);
-#if defined(HAVE_BITS_LIBC_LOCK_H)
+#if defined(HAVE_LIBC_FILE_LOCK)
   DRD_IGNORE_VAR(*(pthread_mutex_t*)(stdout->_lock));
   DRD_IGNORE_VAR(*(pthread_mutex_t*)(stderr->_lock));
 #endif