General fixes

[falkTX]

Just spent some time trying out the high-dpi branch, these are a couple of commits on top of it.

1. make clean was not fully clean
2. disable dpf-based file browser dialog, prevents dependency on dbus (also rtaudio not set to be used on jack standalones, as it is too easy to get feedback loops if we activate the default audio device from the user)
3. fixing some compiler warnings (plus removing some unused freeverb code, which was also giving warnings)
4. no need to get window to call setGeometryConstraints

tested here with standalones and carla lv2 hosting, plugin scales properly.

only the vst3 does not work correctly for high-dpi, but vst3 support in dpf is still experimental anyway.

If you want to try this in carla, easiest way to do it is running QT_SCALE_FACTOR=2 carla from the terminal.
Then make sure it prints this line:

Frontend pixel ratio is 2.0