Add include dir to be able to build with qt source package

This is from 5.3.1 qt source qtdeclarative/
Add private path to includes for desktop qmlc developer build to work
Handle Qt.createComponent for compiled files

Add methods to QQmlEngine which allows one to set a callback that gets called in
place of creating a new QQmlComponent when Qt.createComponent is called from
javascript. We need this so qmlc loader can load the .qmc in place of it
creating new QQmlComponent for the .qml with Qt.createComponent calls.
Merge branch 'qmlc-5.3.1' of https://github.com/qmlc/qtdeclarative into qmlc-5.3.1
Merge pull request #8 from meltingsnowman/qmlc-5.3.1

Handle Qt.createComponent