Reduce duplication in FS path search code

code/qcommon/qcommon.h

@@ -616,8 +616,6 @@ qboolean FS_ConditionalRestart(int checksumFeed, qboolean disconnect);
 void	FS_Restart( int checksumFeed );
 // shutdown and restart the filesystem so changes to fs_gamedir can take effect
 
-void FS_AddGameDirectory( const char *path, const char *dir );
-
 char	**FS_ListFiles( const char *directory, const char *extension, int *numfiles );
 // directory should not have either a leading or trailing /
 // if extension is "/", only subdirectories will be returned