ocaml-nbd: Tidy up spec file

Signed-off-by: Euan Harris <euan.harris@citrix.com>
cmdliner: Rename to ocaml-cmdliner

Signed-off-by: Euan Harris <euan.harris@citrix.com>
SPECS: Great dependency spring-cleaning

In general, an OCaml package's BuildRequires are based on the dependencies
declared in its _oasis file (or similar), and its -devel package's
Requires are based on the dependencies declared in its META file.

* Remove unneeded dependencies
* Add runtime dependencies for -devel packages

Signed-off-by: Euan Harris <euan.harris@citrix.com>
Merge pull request #404 from euanh/split2-merge

SPECS: Great dependency spring-cleaning