Fix letter-spacing in SVG

Qt incorrectly included letter-spacing when WebCore asked us to ignore
it which broke SVG rendering of letter-spaced text in the complex
font path.

Task-number: QTBUG-39601
Change-Id: Ia951e12ac5503955eb0e34e214219f9136c71465
Reviewed-by: Julien Brianceau <jbriance@cisco.com>
Reviewed-by: Michael Bruning <michael.bruning@digia.com>