Initial changes qucs-attenuator Qt4 only.

Trying to get rid of Qt3Support.
Small fix, cleanup

Fix the layout of the help dialog.
Remove unused includes and forward declarations.
Done porting qucsattenuator to Qt4.

Compiled without Qt3Support.
Testes on a Mac. I'm not sure about the menubar space.
It also doens't update the layoutsize when changing from
Bridged Tee to Tee, only when go up to Pi again.
Merge pull request #18 from guitorri/qucsattenuator_qt4

Qucsattenuator qt4