To create the kindle version:

    * build programs
    * build pre

    * kindlegen's archive in ~/xfer
    * md tmp/kindlegen, extract the archive

    * cd bin 
    * createhtml
    * cd html
    * edit cplusplus.mobi to reflect the latest version, maybe add a new
        chapter. 
    
    * ../tmp/kindlegen/kindlegen -gif cplusplus.opf

    * Follow the instructions at
        https://kdp.amazon.com/self-publishing/dashboard 
      for uploading the latest version

    * cd ..
    * build distclean