ProParser: Fix build with MSVC

Strangely, MSVC requires operator< for values of std::list.

Change-Id: I5f62348a69d9b25585798b7824c6538d4cb5df7c
Reviewed-by: hjk <hjk@qt.io>

src/shared/proparser/proitems.h

@@ -257,6 +257,15 @@ inline ProStringList operator+(const ProStringList &one, const ProStringList &tw
 
 typedef QHash<ProKey, ProStringList> ProValueMap;
 
+// For std::list (sic!)
+#ifdef Q_CC_MSVC
+inline bool operator<(const ProValueMap &, const ProValueMap &)
+{
+    Q_ASSERT(false);
+    return false;
+}
+#endif
+
 // These token definitions affect both ProFileEvaluator and ProWriter
 enum ProToken {
     TokTerminator = 0,  // end of stream (possibly not included in length; must be zero)