Add virtual "Qt.widgets" module for Qt 4 installations.

We used to have this when we still hardcoded all the modules, and it got
lost during the switch.

Change-Id: I3170a2ca77f0a105b1b6c7de485be6d112bf88e7
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
Allow dependencies on "Qt.test".

That's what we called the "testlib" module until recently, so let's keep
supporting that name.

Change-Id: I324c9b3add0a8709dba8b84458189727df9cf6d2
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>