Cleanup spec file and allow build tar without SELinux
    
    - repair the xattr-gnulib-prepare patch to allow build tar without SELinux
      support
    - fedora-review compliance -> remove trailing white-spaces, remove macro from
      comment, remove BR of gawk;coreutils;gzip that should be covered automatically
      by minimum build environment, do not `rm -rf' buildroot at the beginning of
      install phase (needed only in EPEL), remove BuildRoot definition, remove
      defattr macro, s/define/global/
    - do not use ${VAR} syntax for bash variables, use just $VAR