Fix Qt 4 compilation.

See next commit.
Replace all uses of QT_VERSION_CHECK with explicit version.

Qt4's moc is not able to expand QT_VERSION_CHECK which may lead
to invalid codegen when used for backwards compatibility work.
Replaced all occurances with explicit check against numeric
version which are treated correctly. Even though bad interactions
might be rare we should no longer use this macro as long as we
want to compile with Qt 4. Also see:
http://lists.qt-project.org/pipermail/interest/2013-August/008351.html