• Made the Clone module a hard requirement, so we don't have to
  provide a fallback function for HTTP::Headers::clone().
  We require at least Clone 0.46, as that release now supports
  Perl back to 5.8.1, just like us. (GH#184) (Neil Bowers)
  
• Import clone from Clone rather than inheriting (GH#189) (Graham Knop)
  
• Made the Compress::Raw::Zlib 2.062 module minimal required
  version. (GH#190) (Jakub 'q84fh' Skory)