forgot changelog
Use RPM macros for all dirs, instead of assuming the layout under %_topdir

Before this change, CPANPLUS::Dist::Mageia assumes there will be a
layout %{_topdir}/{BUILD,RPMS,SOURCES,SPECS,SRPMS,tmp}, but rpm allows and
supports customisation of all of these locations via the macros:
- %{_builddir}
- %{_rpmdir}
- %{_sourcesdir}
- %{_specdir
- %{_srpmsdir}
- %{_tmppath}

If the directory layout CPANPLUS::Dist::Mageia expects does not exist,
the error:
[ERROR] Format 'CPANPLUS::Dist::Mageia' is not available
even though the subsequent rpmbuild commands would work.

This patch corrects that, by using the locations for _builddir, _rpmdir,
_sourcesdir, _specdir, and _srpmsdir. _tmppath is not strictly required,
since the %buildroot macro is created from _builddir.

It is debateable whether _builddir should be added or not, as the module
itself does not write or read any files from the location built from
this macro (as it does for rpm,source,spec,srcrpm).
v1.121710

 - use rpm macros for all dirs (buchan milne)
insert an empty description instead of "no description found"
new readme file generated by dzpba-jquelin
v2.000

 - insert an empty description instead of "no description found" to make
   sure rpmlint catches the error
License should be more standard.

See:

http://fedoraproject.org/wiki/Packaging/LicensingGuidelines .

License should read "GPLv1+ or Artistic" instead of "GPL+ or Artistic".
rpmlint complained about that.
Add double dashes for M-B-Tiny compat.

The double dashes ("--") are for Module::Build::Tiny compatibility:
     * https://rt.cpan.org/Ticket/Display.html?id=86240
     * https://wiki.mageia.org/en/Perl_policy

BTW, shouldn't we use Module::Build whenver there's a Build.PL even if
a Makefile.PL does not exist?