Fixup wrong merge: remove src/qt/src

This reapplies the patch of issue #11590 and drops the patch
from issue #11264. The former is still valid, while the latter
is hopefully resolved properly in Qt5 (see e.g. this:
https://bugs.webkit.org/show_bug.cgi?id=69419).

https://github.com/ariya/phantomjs/issues/12427
Merge pull request #12428 from KDAB/cleanup_qt5merge

Fixup wrong merge: remove src/qt/src