control file can express arch dependent build dependencies

[Dominique Dumont <domi.dumont@free.fr>]

Hello Jawnsy

Looks like the dependency parsing of libdebctrl will be even more complex. 

You'll see in this enclosed mail that arch-specific build-dependencies can be 
expressed like:

    super-duper-3rd-party-lib [i386 amd64]

So you'll have to take this into account in your control.h strucutures and 
your parser

All the best