QmlJS: Change from QMap to QHash for QString keys.

Tests indicate that lookup in QHash<QString, ...> is more performant
even for short strings.

Change-Id: I8e5a73d0f1a72e202522f397b16901887f9c3591
Reviewed-on: http://codereview.qt-project.org/5070
Reviewed-by: Leandro T. C. Melo <leandro.melo@nokia.com>

src/libs/qmljs/qmljsmodelmanagerinterface.h

@@ -114,7 +114,7 @@ public:
     {
     public:
         QList<LanguageUtils::FakeMetaObject::ConstPtr> exportedTypes;
-        QMap<QString, QString> contextProperties;
+        QHash<QString, QString> contextProperties;
     };
 
     typedef QHash<QString, CppData> CppDataHash;