SDL: Default audio output rate to 44kHz.

As the title suggests this makes SDL ports use a default of 44kHz instead of 22kHz for the audio output rate. GP2X, Symbian, WinCE still use their old default values. This should increase the sound quality for games. This includes the AdLib emulator, but is probably also beneficial for Wintermute games.

For desktop ports it should be no issue to default to 44kHz. The only issue might be lower end ports derived from SDL. This includes MAEMO, Dingux, GPH (only GP2x Wiz), OpenPandora, WebOS, SamsungTV and LinuxMoto (and PS3, but I guess it should be fine). If you are a porter of any of these ports and have an opinion/objection about this change, please drop a line in here. I will wait for a week and merge this (somewhen next sunday) in case no objections have been raised by porters.