Dear Maintainer,

I'm trying to cross build some code that uses libbfd (not for Debian).
However, I can't install binutils-dev:${foreign-arch} because is depends
on binutils.

In #842439, all libraries previously provided by binutils have been
moved to the (then new) libbinutils binary package. At that time,
binutils-dev was changed to depend on both binutils and libbinutils.
However, that dependency on binutils is no longer needed since nothing
in binutils-dev really uses what's left in binutils itself (basically
just the programs).

Beyond dropping that dependency, adding `Multi-Arch: same` makes a
foreign binutils-dev co-installable with a native one.

The attached patch does both things.

Control: tags -1 + moreinfo
Control: tags -1 - patch

 - bfd.h is architecture specific
 - binutils-dev stores the test results from the
   testsuite in a common place.

I didn't check what would break when moving the header files to the MA include dir.

Please base patches on the binutils package from experimental.

Matthias