[ioquake3] mumble link support

[Ryan C. Gordon]

>>> Can someone make a decision on Ludwig's Mumble support? I'd like to 
>>> update my VoIP patches, but they need to take cl_useMumble into
>>> account, so this has to go in to Subversion first if it's going in.

I have updated my VoIP patch in Bugzilla to match Ludwig's Mumble 
support that went into Subversion.

I would really love for someone to update the non-OpenAL mixer to handle 
multiple streams in S_Base_RawSamples(), so I don't have to do it. 
Without that, non-OpenAL users won't hear any incoming VoIP.

We also need a non-OpenAL path for recording audio, but as that doesn't 
exist in SDL (yet...it's going into 1.3), I'm not sure what to do there 
if we don't want to maintain platform-specific code. I'm sort of the 
opinion that you should just use OpenAL if you want to talk into a 
microphone, though.

And, of course, a real UI for VoIP would be nice, but I have no plans to 
do this myself.

--ryan.