Adjust valgrind run to fail tests if valgrind report errors.

configure.ac

@@ -63,7 +63,7 @@ then
   AC_PATH_PROG(VALGRIND,valgrind,)
   if test "x$VALGRIND" != "x"
   then
-    VALGRIND="$VALGRIND -q --leak-check=full --show-reachable=yes --num-callers=50"
+    VALGRIND="$VALGRIND -q --error-exitcode=99 --leak-check=full --show-reachable=yes --num-callers=50"
     TESTS_INFO="Test suite will be run under:
     ${VALGRIND}"
   else