QmlJS: Fix semantic and non-semantic QML error reporting.

The QML snapshot only ever contains valid Documents; to compile a list
of parser problems we need to get at the invalid documents.

To do that, the model manager now provides a Snapshot with up to date,
but potentially invalid documents. That should also be useful for other
things.

Change-Id: I67892f63771c221bf2fe2c2bf0240a0f4e523227
Reviewed-on: http://codereview.qt.nokia.com/3012
Reviewed-by: Fawzi Mohamed <fawzi.mohamed@nokia.com>

src/plugins/qmljstools/qmljsmodelmanager.h

@@ -69,7 +69,7 @@ public:
     void delayedInitialization();
 
     virtual WorkingCopy workingCopy() const;
-    virtual QmlJS::Snapshot snapshot() const;
+    virtual QmlJS::Snapshot snapshot(bool preferValid = true) const;
 
     virtual void updateSourceFiles(const QStringList &files,
                                    bool emitDocumentOnDiskChanged);
@@ -126,7 +126,8 @@ private:
 
     mutable QMutex m_mutex;
     Core::ICore *m_core;
-    QmlJS::Snapshot _snapshot;
+    QmlJS::Snapshot _validSnapshot;
+    QmlJS::Snapshot _newestSnapshot;
     QStringList m_allImportPaths;
     QStringList m_defaultImportPaths;