## Localisation

The format of the message catalog is as follow:

     line       : '#' comment              # a comment
                | tag ':' definition       # a tag definition
                | tag '=' tag              # a link to another tag
                | '[' prefix ']'           # a prefix to append to other tags

     prefix     : tag                      # the tag to use as prefix
                | '*'                      # don't use a prefix

     definition : string                   # a string
                | string '\' definition    # with posibility of continuation '\'

     tag        : [a-zA-Z0-9_]+