Integer-overflow in QFixed::QFixed

1. Have a build of Qt configured with "-sanitize undefined".
2. Build the attached project.
3. Run the resulting program and pass the input file:

   ./report 26034.html
   

   You will see output like:

   /work/qtbase/include/QtGui/6.0.0/QtGui/private/../../../../../../../src/qt/qtbase/src/gui/painting/qfixed_p.h:66:37: runtime error: signed integer overflow: 80000000 * 64 cannot be represented in type 'int'
   

Found by oss-fuzz as issue 26034.