RFC: introduce common.m4

[Tom Tromey]

>>>>> "Pedro" == Pedro Alves <palves@redhat.com> writes:

[ old-ish thread... ]

Pedro> IMO, it's a little better if each subdirectory treats the
Pedro> others more as black boxes.  gdb/ relying on common/'s
Pedro> HAVE_FOO checks feels like gdb/ relying on common/'s
Pedro> implementation details to me.  But I don't want to impose.

Yeah, I agree.  When I refresh this patch I will do it this way.

Lately I have been thinking that common and gdbserver should be
top-level directories (after renaming "common" something more suitable).
This would let us use libiberty in gdbserver while still preserving, I
think, the ability to build gdbserver separately.  Also it would let us
treat "common" as a true library, not as the odd beast it is today.

Perhaps gnulib would also have to be pushed up.

Tom