[SDL] bug in SDL_mixer 1.2.8, function _EFF_PositionDeinit(effect_position.c)

[Dietfrid Mali]

_EFF_PositionDeinit doesn't reset the position_channels counter and should look
like this:

void _Eff_PositionDeinit(void)
{
    int i;

	 if (pos_args_array) {
		for (i = 0; i < position_channels; i++)
			  free(pos_args_array[i]);
	    free(pos_args_array);
		 pos_args_array = NULL;
		}
	 position_channels = 0;
	 if (pos_args_global) {
		free(pos_args_global);
		pos_args_global = NULL;
		}
}