[Qt] Time to go to 4.3?

[Felipe Monteiro de Carvalho]

Hi, I removed the define now.

I think that from now on we can support just 1 Qt version at a given
time (or superior).

But please go slow when the next Qt comes out. Wait at least until a
couple of linux distributions are using it before changing.

thanks,
-- 
Felipe Monteiro de Carvalho