QmlJS: Fixing warnings

Correcting ImportKey::compare(). The compare function was not stable
and QMap did not work properly.

Done with: Fawzi

Change-Id: I11790215cba6944bf9f04be0c3844b35ea54ea70
Reviewed-by: Fawzi Mohamed <fawzi.mohamed@digia.com>

src/libs/qmljs/qmljsimportdependencies.h

@@ -223,6 +223,7 @@ public:
 
     QSet<ImportKey> libraryImports(const ViewerContext &viewContext) const;
     QSet<ImportKey> subdirImports(const ImportKey &baseKey, const ViewerContext &viewContext) const;
+    void checkConsistency() const;
 private:
     void removeImportCacheEntry(const ImportKey &importKey, const QString &importId);