sexplib.7.0.2 requires ocaml<4.00 due to toplibs

part of triage run in OCamlPro/opam-repository#1029
fix odisco zip dependency change in 76cd3e3e386410db33c747ca8f7fbaa33e4816ae
zip -> camlzip
vhd-format: tighten up constraint as it fails with cstruct.0.6.0
Merge branch 'ocamlot-triage-20130830' of github.com:mirage/opam-repository into ocamlot-triage-20130830
flow: depend on a specific version of core to ensure that the CLOEXEC patch gets picked up on 4.1

This isn't really a fault of the Flow package, but the constraint solver (see OCamlPro/opam#789)
facile: add patch to not invoke make directly but use $(MAKE) to improve BSD compat

found as part of triage run in OCamlPro/opam-repository#1029