mention last changes

  DCL compatible exit code.  This fix required the enhancement described next.

  This also adds an enhancement to main.c so that when curl is run under a

  Unix shell like Bash on VMS, it will return the standard Unix exit codes

  and messages."

  and messages." And another patch for docs/examples.

  I introduced os-specific.c and os-specific.h for use in curl tool code

  and adjusted John E. Malmberg's patch placement to use these new files