QT_VERSION is now defined via QT_VERSION_CHECK

Since https://codereview.qt-project.org/#/c/126105/, the QT_VERSION define is now an expansion of the QT_VERSION_CHECK macro, but moc doesn't process this macro. The result of this is that a signal or slot can no longer have a signature that is conditional by checking QT_VERSION, e.g.

signals:
#if QT_VERSION >= 0x050000
void incomingConnection(qintptr descriptor);
#else
void incomingConnection(int descriptor);
#endif

works as expected with Qt < 5.7, but no longer compiles with Qt 5.7 as moc and gcc end up using different signatures.

This is using qmake, on x86_64. I think I have traced this to the fact that x86_64 isn't defined when moc is run, but it is when gcc runs. This means __WORDSIZE gets defined incorrectly and moc tries to include qconfig-32.h instead of qconfig-64.h