Various fixes and FreeBSD modifications:

Various fixes and FreeBSD modifications:

. remove the blubber about `submitter-id's from the man page, we don't
  use them,
. use REPLY_TO or REPLYTO in preference over LOGNAME as the value for
  the Reply-To address (closes PRs 1471 and its duplicates 1472 and 1823),
. don't abuse ~/.signature as ORGANIZATION, this is almost always
  useless blunder,
. actually list the Categories again, instead of xrefing to ``see
  above'' (closes PR 1835),
. check the Synopsis field for being not empty,
. make the mail Subject the same as Synopsis if left blank (closes
  PR 1209).

The remaining open send-pr related PRs (184 and its duplicate 1047,
and 1415) are pilot errors or local hardware problems.