[IMPLEMENTED] Qt4 support (Gambas3)

[Ayortano]

Hello! I've been thinking that I will begin to bear Xt7 to Gambas3, because I think it is quite mature, and Qt4 too. It was only to warn, and if someone wants to give me any specification, please do so.

Greetings from Uruguay

[kokoko3k]

Thank you so much for you interest, i've made some tries in the past, and my issues was with
- the system tray icon causing a runtime error (now appears to work)
- drag'n drop operations on the chains window, the driver window and the filter configuration window.
- Some problem in the mplayer class routine because of handling of external processes via SHELL/INPUT/OUTPUT/READ/WRITE Keywords that didn't work as expected.
Apart from them, some symbols are changed between gambas2 and 3, but that's easy to correct.

Considering that major distribution doesn't ship gambas3 yet and that those issues could be corrected by upstream instead of finding workarounds, i've decided to wait for a stable version, anyway if you want to work on it anyway,
you're welcome.