[mythtv] ALSA patch

[James Knight]

Ok, so I haven't quite finished hacking up MythMusic as I've been 
busier than expected, but here's a (*working as far as I have tested*) 
patch to add a layer for generic audio out support, as well as drivers 
for both standard /dev/dsp and libalsa to libmyth.

Here's the basics of the patch:
libs/libmyth/ contains new files:
AudioOutput.cpp/.h: Virtual base class.
AudioOutputDSP.cpp/.h: Implementation of AudioOutput that uses the 
standard /dev/dsp output
AudioOutputALSA.cpp/.h: Implementation of AudioOutput that uses libalsa

AudioOutput.patch patches:
libmythtv/NuppelVideoPlayer.cpp/.h: removed all DSP audio output code 
and use the AudioOutput class instead.
settings.pro: added CONFIG += using_alsa
libs/libmyth/libmyth.pro: added new sources and headers.

There is no way to select ALSA output via the configuration interface 
yet, so you'll have to set it manually in the database. Set the 
"AudioOutputDevice" configuration parameter to "ALSA:<alsadevice>". So, 
for most people, set it to "ALSA:default".

You can compile without ALSA support (if you don't have the libraries 
or whatever) by commenting out "CONFIG += using_alsa" in settings.pro.

NOTE (especially for Craig Longman, since I know you're working on the 
Reencode stuff right now): I significantly changed how the ReencodeFile 
audio works, but I *HAVEN'T* tested it at all, as I'm not sure how to 
do so. It "should" work.

I've been using this code for the last couple weeks so I know it at 
least mostly works. I'm probably not going to be able to read email for 
the next week and a half, so if you have any comments I won't be able 
to respond till then.

James