restrict ocamlspot to compiler versions <4.01.0 since it needs a new release there

triaged as part of OCamlPro/opam-repository#1029 regress run
omake upstream is offline (dns failure), so redirect source to Fedora mirror of archive instead (same checksum)
websocket: add constraint on cohttp.0.9.10+

see vbmithr/ocaml-websocket#9 and OCamlPro/opam-repository#1029