UPBGE: Set audiorate to 48000Hz by default

48000Hz is the newer standard used in professional audio recording as it
"works" better with multiple frame rates.

Additionally, it solves the frequent "Error AL lib: UpdateDeviceParams:
Failed to set 44100hz, got 48000hz instead" raised in a lot realtek,
intel, nvidia integrated sound cards (some of them even with crash).

And it seems to works better with HRTF binaural sound (in me own TODO
list)

TODO: To make this value configurable by user

source/gameengine/GamePlayer/GPG_ghost.cpp

@@ -771,7 +771,7 @@ int main(int argc,
 	// XXX add the ability to change this values to the command line parsing.
 	U.mixbufsize = 2048;
 	U.audiodevice = 2;
-	U.audiorate = 44100;
+	U.audiorate = 48000;
 	U.audioformat = 0x24;
 	U.audiochannels = 2;