removal of qt3support

From the pull #152 in master of today the state of removal qt3support is:
*** FULLY REMOVED ***

I have not added any bugs, but needed tester.

The only thing left is to change the class QWorkspace (obsolete but qt4) for QMdiArea

Rallaz

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Great job!

I found I couldn't really remove qt-qt3support package on gentoo still. qt3support still required for many applications, so, librecad is still among early adopters.