Added support for recognizing invalid mutexes.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@7497 a5019735-40e9-0310-863c-91ae7b9d1cf9
diff --git a/exp-drd/drd_clientreq.h b/exp-drd/drd_clientreq.h
index bb701e2..b035713 100644
--- a/exp-drd/drd_clientreq.h
+++ b/exp-drd/drd_clientreq.h
@@ -119,6 +119,7 @@
 
 typedef enum
 {
+   mutex_type_invalid_mutex    = 0,
    mutex_type_recursive_mutex  = 1,
    mutex_type_errorcheck_mutex = 2,
    mutex_type_default_mutex    = 3,