Support synthesized oblique and bold in SceneGraph

Support synthesized oblique and bold in SceneGraph

When fetching the outlines we need to synthesize the weight and
style of the requested font. This is currently only supported
on FreeType versions that have the Embolden and Oblique functions.
We also use FreeType's Oblique function for regular text when
possible, and only use the matrix approach when that function
is unavailable.

Task-number: QTBUG-21202
Change-Id: I0656ab66cc3ec70d6a7675b8c78d06632625261c
Reviewed-on: http://codereview.qt-project.org/5076
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Jiang Jiang <jiang.jiang@nokia.com>