Merge pull request #259 from euanh/build-improvements

xapi: Update to 1.9.30
ocaml-syslog: Remove package

This package is unmaintained and we no longer need it.
Originally it came from Godi, which is gone; for a while
we got it from OPAM's archive but it has also been removed
from there.

Signed-off-by: Euan Harris <euan.harris@citrix.com>