Added new macros for checking QTWEBKIT version.

QTWEBKIT_FROM_2_2 - >= 2.2.0
QTWEBKIT_TO_2_2   - < 2.2.0
QTWEBKIT_FROM_2_3 - >= 2.3.0
QTWEBKIT_TO_2_3   - < 2.2.0

It also check whether Qt5 is used and if so, it will
compile all features just like the QtWebKit version
was 2.3.0