[Fedora-packaging] Adjust old ruby guidelines to new ruby guidelines

[Till Maas]

Hi,

I noticed that the old ruby guidelines[0] and the new ruby guidelines[1]
use different macro names, for example gemname and gem_name. Since the
old guidelines need to be used for several years in EPEL, I propose to
adjust the old guidelines to the new guidlines as much as possible:

- use consistent macro names
- define macros provided in rubygems-devel in F17+ in spec files
  according to the old guidelines

Are there any general objections? Otherwise I will prepare a Packaging
Draft with above changes.

Regards
Till

[0] https://fedoraproject.org/wiki/Packaging:Old_Ruby
[1] https://fedoraproject.org/wiki/Packaging:Ruby