Improve adherence with current Fedora packaging guidelines
- Add support for DESTDIR.
- Remove extra license patch in order to use %license.
- Make usage of scriptlets %make_build, %make_install and
%ldconfig_scriptlets.
- Prevent unintentional soname bumps by specifying it via %soname.
- Use %global instead of %define for %{cpu_variants}.
- Remove unintentional usage of %{_isa}.