QmlJS: Rename Interpreter::Engine -> ValueOwner

Also move to a separate file.

Change-Id: I05910e8cf04a533b5d09a1c16e612e3b99b1d606
Reviewed-on: http://codereview.qt.nokia.com/1039
Reviewed-by: Fawzi Mohamed <fawzi.mohamed@nokia.com>

src/libs/qmljs/qmljsscopebuilder.cpp

@@ -126,10 +126,10 @@ void ScopeBuilder::initializeRootScope()
 
     scopeChain = ScopeChain(); // reset
 
-    Interpreter::Engine *engine = _context->engine();
+    Interpreter::ValueOwner *valueOwner = _context->valueOwner();
 
     // ### TODO: This object ought to contain the global namespace additions by QML.
-    scopeChain.globalScope = engine->globalObject();
+    scopeChain.globalScope = valueOwner->globalObject();
 
     if (! _doc) {
         scopeChain.update();