ocaml-xcp-idl: Add install dependency on message-switch

Note this dependency is added to the -devel package.

Signed-off-by: Euan Harris <euan.harris@citrix.com>
xe-create-templates: Add dependency on ocaml-xcp-idl-devel

Also fix misleading URL field.

Signed-off-by: Euan Harris <euan.harris@citrix.com>
Merge pull request #238 from euanh/debian

Fix build problems on Ubuntu