version:add-spec

• (version:add-spec spec revision) -> void
      spec : any scheme value
      revision : any scheme value

  These two values are appended to the version string. write is used to transform them to strings. For example:

  (version:add-version-spec 's 1)

  in version 45 will make the version string be "45s1". The symbols 'f and 'd are used internally for framework and drscheme revisions.