specs: Don't build debuginfo subpackages for OCaml code

Debuginfo subpackages aren't actually built for OCaml packages,
but the Python RPM library thinks they will be built so makemake.py
produces build rules for them.   Since the targets of the rules are
never actually built, these packages may be rebuilt unnecessarily
during subsequent builds.

The example spec file given in the Fedora OCaml packaging guidelines:

   https://fedoraproject.org/wiki/Packaging:OCaml

Note that the example uses %define (lazily expanded), whereas we are using
%global (eagerly expanded, available in global context).   A comment in
ocaml-re.spec (from upstream) suggests that it is better to use %global
than %define.

Signed-off-by: Euan Harris <euan.harris@citrix.com>
Merge pull request #225 from euanh/build-improvements

specs: Don't build debuginfo subpackages for OCaml code