... and add "MAILINDEX".

As described in #2789, this is a suggested solution.  Changing UID=xx to
actually get mail with UID xx and add "MAILINDEX" to get a mail with a
special index in the mail box (old behavior).  So MAILINDEX=1 gives the
first non deleted mail in the mail box.

Fixes #2789
Closes #2815

Updated the reply data in tests: 800, 801, 802, 804 and 1321 to possess
the CRLF as per RFC-822.

Added one test for a request with matching UIDVALIDITY and one which is
a mismatched request that will fail.

Continued segregating the email protocol tests, into their own protocol
based ranges, in preparation of adding more e-mail related tests to the
test suite.

They were all wrong previously since none used the <brackets> they
should for MAIL FROM. Now libcurl adds them itself if the app doesn't so
they end up wrong less easy.

  properly in angle brackets. Recipients provided with CURLOPT_MAIL_RCPT now
  get angle bracket wrapping automatically by libcurl unless the recipient
  starts with an angle bracket as then the app is assumed to deal with that
  properly on its own.

  in the same RCPT TO line, when they should be sent in separate single
  commands. I updated test case 802 to verify this.

- I also fixed a bad use of my_setopt_str() of CURLOPT_MAIL_RCPT in the curl
  tool which made it try to output it as string for the --libcurl feature
  which could lead to crashes.

user name