`binary' target and per-architecture rebuilding

[Ian Jackson <ian@chiark.chu.cam.ac.uk>]

In order to solve some tricky problems to do with
architecture-independent files being produced and uploaded as a result
of per-architecture porting builds, I'm splitting the `binary' target
into two:

binary-arch will build the architecture dependent binary packages and
files.  For a straightforward architecture-dependent package this is
usually all the work.

binary-indep will build architecture-independent binary packages and
files.  For a completely architecture-independent package this is all
the work.

binary will remain, and simply do one and then the other.

Ian.