TextEditor: get CompletionAssistProvider from editor.

And not from the global object pool. This way, the editors that have
different highlighters for various language dialects, or editors that
support multiple languages in a single editor, can decide themselves on
what CompletionAssistProvider to provide.

Change-Id: Ieebc4a8e7b3de6470fdb8103035aa3b8b2ba6598
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>

src/plugins/texteditor/codeassist/codeassistant.h

@@ -62,6 +62,9 @@ public:
 signals:
     void finished();
 
+public slots:
+    void reconfigure();
+
 private:
     CodeAssistantPrivate *d;
 };