devel/gdb: make this build on NetBSD/macppc.

* Follow up struct member renames in callframe and stackframe.
* Import fixes to ppc-nbsd-tdep.c from our in-tree gdb.
* Fix up sim/ppc/emul_netbsd.c to use the versioned syscall names
  for gettimeofday and getrusage.

Bump PKGREVISION.

(he)