(svn r2728) -Fix/Feature: Change the driver probing algorithm

Instead of trying to start a single driver and bailing out if that fails, try to initialise one by one and use the first one which succeeds.
This should fix problems on machines with no sound card, where -s null had to be specified manually.

functions.h

@@ -273,7 +273,6 @@ void LoadFromConfig(void);
 void SaveToConfig(void);
 void CheckConfig(void);
 int ttd_main(int argc, char* argv[]);
-byte GetOSVersion(void);
 
 void DeterminePaths(void);
 char * CDECL str_fmt(const char *str, ...);