[PATCH] stream mapping reloaded

Well this was about to be a patch for mplayer's version of libdvdread, because 
i noticed that subpicture/audio stream mapping is ignored by mplayer. 

So I created some structures, and wrote the corresponding                        
code for mplayer, only to realize that ogle uses the mapping info, but as a 
whole 32/16 bit integer, and using bit operations to get out the necessary 
numbers.

However if you think that my version is a nicer way to manage this information 
(IMHO using bitfields is certainly more descriptive than something like x >> 
24 & 0x07), please feel free to apply these patches (diff is from the cvs 
version).

Regards,
Lehel