Fix initialiser in C++ test: MSVC++ cannot assign statically to non-static members.

tests/run/cpp_operators_helper.h

@@ -84,10 +84,12 @@ NONMEMBER_BIN_OP2(COMMA)
 #define REF_BIN_OP(op) int& operator op (int x) { x++; return value; }
 
 class RefTestOps {
-    int value = 0;
+    int value;
 
 public:
 
+    RefTestOps() { value = 0; }
+
     REF_UN_OP(-);
     REF_UN_OP(+);
     REF_UN_OP(*);