qdoc doesn't recognize Q_REVISION macro

qdoc is not handling the Q_REVISION macro properly. Consequently the doc bot complains whenever we submit a patch that contains a revisioned slot or signal, for example this change:

https://codereview.qt-project.org/#change,49777

qtbase/src/gui/kernel/qwindow.h:286: warning: No documentation for 'QWindow::Q_REVISION()'

And the actual output docs contain several signals like this:

QWindow::Q_REVISION() [signal]

when the source looked like this

Q_SIGNALS:
...
Q_REVISION(1) void minimumWidthChanged(int arg);

Slots can have revisions too, like this

Q_REVISION(1) void setMinimumWidth(int w);

And properties can be declared with revisions, like this:

Q_PROPERTY(int minimumWidth READ minimumWidth WRITE setMinimumWidth NOTIFY minimumWidthChanged REVISION 1)

but the property declaration is not causing any trouble.