Added .qdoc extension to the cppeditor's mime types.

src/plugins/cppeditor/CppEditor.mimetypes.xml

@@ -43,6 +43,7 @@
         <glob pattern="*.c++"/>
         <glob pattern="*.C"/>
         <glob pattern="*.inl"/>
+        <glob pattern="*.qdoc"/>
     </mime-type>
 
     <mime-type type="text/x-objcsrc">