SunOS4 is missing memmove

[Tom Tromey]

>> libjava refuses to configure when memmove is missing.

Per> I thought we were linking in libiberty, which provides memmove.
Per> If we're not, perhaps we should;  that is what libstdc++ does
Per> (or at least used to).

We don't link it in.  libstdc++ got in trouble here since parts of
libiberty are GPLd; maybe we should just avoid it.

I think we were picking up memmove from newlib on embedded targets,
and assuming it would be in libc on natives.

Tom