elfutils.spec.in: Sync with fedora spec, remove rhel/fedora specifics.

elfutils.spec.in: Sync with fedora spec, remove rhel/fedora specifics.

This makes the sample elfutils.spec file more like the fedora
elfutils.spec but with all fedora and rhel specifics removed.
In particular it introduces a new elfutils-libs subpackage and
updates the requires accordingly.

Other cleanups are removal of Group tags, remove dot at end of
Summary tags, add post/postun ldconfig for elfutils-libs and
elfutils debuginfod-client subpackages, remove default
defattr(-,root,root) for file lists and order binaries by name.

Signed-off-by: Mark Wielaard <mark@klomp.org>