#28 controls for unavailable operations should be disabled

[quadrispro]

While using gnome_wave_cleaner, some operations could not be available (ogg support, mp3 support, etc) but the related GUI controls are still visible and enabled. This may cause confusion as clicking on those controls doesn't have any effect.

Thanks in advance.

[Alister Hood]

First, to clarify what is described:
- Ogg and mp3 read support are broken, but don't have any gui controls.
- Ogg and mp3 export are always compiled in, and just need to be configured in gwc as they use external binaries. Yes, ideally we would find them automatically, instead of configuring it manually, and true, they may not be available, but if we check for their presence and hide the controls, how will the user know these features exist? I am open to any sensible patches, but otherwise these are a "won't fix" for me - it isn't worth spending time on.

Second, one thing that is confusing (so we should really hide it when appropriate) is the configuration of the audio device, which is only relevant when compiled against the alsa backend. A patch or pull request to deal with this would be great, as I'm otherwise unlikely to find the time to deal with it in the near future. Even better would be reworking it to build the audio backends as plugins so you can build more than one and configure in gwc which one to use.