Qt5 linux

In fact only 3 patches are needed to fix the Linux build on the qt5 branch. They are modifing build, linking and installation. Too bad the current master branch is broken. You should have also branched libkeyfinder. Are you planning to fix the master branch, or drop the qt4 dependency and replace it with qt5?

P.S.:

I am currently working on fixing the warnings / porting to the new api of libav. This contains porting things to libavresample. I am doing this because I got errors while resampling ogg and mp3 files. (only wav and flac don't seem to need resampling).
I did this on the master branch, but I will rebase the changes to the qt5 branch.

Cheers, and nice software you got there.