Spec clean-up
    
    - Add provides filters that work with all supported distributions
    - BR: perl(Carp) and perl(Exporter)
    - Make %files list more explicit
    - Drop explicit requires of perl(Exporter) since it's auto-detected by rpm
      4.9 onwards, and is bundled with perl on all older distributions
    - Don't need to remove empty directories from buildroot
    - Don't use macros for commands
    - %defattr redundant since rpm 4.4
    - Use tabs