qt-5.3: added attrPath="qt53Full" and "attrPath="qt53"; qt-5.2 still default

what i did:
- i added qt 5.3 (kind of a version bump of qt 5.2)
- i built qt53 and qt53Full (both compile & install)
- i've been using qt53 to compile the google game voltair and it worked

warning: qt 5.2 is still the default qt5