CppTools: Add some methods to the JsExpander.

Make some C++ related methods available to the JsExpander. These
are concerned with namespace handling, etc.

Change-Id: I2fc3807cf421b817bb103b727606a78aee290652
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>

src/plugins/cpptools/cpptools.qbs

@@ -67,6 +67,7 @@ QtcPlugin {
         "cpptools.qrc",
         "cpptools_global.h",
         "cpptoolsconstants.h",
+        "cpptoolsjsextension.cpp", "cpptoolsjsextension.h",
         "cpptoolsplugin.cpp", "cpptoolsplugin.h",
         "cpptoolsreuse.cpp", "cpptoolsreuse.h",
         "cpptoolssettings.cpp", "cpptoolssettings.h",