patch for compiles that don't define "unix"

[Stan Shebs]

Fernando Nasser wrote:
> 
> Don't feel sorry.  Many of us have ARM boards (or boards with the
> ARM Angel monitor on it) and we are only able to use GDB on it
> because the rdi-share directory is in there.  This protocol is
> hard to implement and it would take a while until someone would
> contribute one written from scratch.

That was my thinking too, but it ended up taking as much time to get
the code working with GDB as it would have taken to start from
scratch - rdi-share has piles of pointless generality.  The protocol
isn't completely implemented either, and the part that does get
used isn't that complicated.  Look at remote-rdp.c, it's actually
quite similar (which shouldn't be a surprise, because it's what talks
to ARM's previous generation of boards).

Stan