#42 - Delphi.build() method supports non-numeric delphi version ("XE", "XE2" etc)

 - symbolic constants added for Delphi versions (internal, numeric versions)

 - DelphiVersion() method to map "delphi" options flag to DELPHI_XXX version

 - DelphiVersionName() method to provide human meaningful name of DELPHI_XXX version number
Merge branch 'master' of https://github.com/deltics/train