Avoid fontconfig access in fontEngine creation

Avoid fontconfig access in fontEngine creation

The only thing we need to know at fontEngine creation is the hinting
style, we can just store it in enumeration process and get it back
from user data pointer. So that fontEngines can be created without
access to fontconfig at all. (Since we are doing our own matching.)

Change-Id: I5ab2d1f27e28787447aedcbdef16555fb0f1b604
Reviewed-on: http://codereview.qt-project.org/4769
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Jiang Jiang <jiang.jiang@nokia.com>