As Aaron Schrab noted, patch-0.95.6.tlr.reverse_name.1 broke the use

As Aaron Schrab noted, patch-0.95.6.tlr.reverse_name.1 broke the use
of my_hdr from send-hooks.  This patch introduces a new variable
$from which can be used to use a default sender address; to make
this possible, a new variable class DT_ADDR is defined.

We now have the following algorithm for determining the from
address:

- $from is used as the default from address, if defined.  Otherwise,
  the local user name and (if the user wishes so) the local domain
  are used.
- This address can be overridden by $reverse_name, if set.
- Now, send-hooks are evaluated.
- Afterwards, user headers are evaluated.  In this step, the from
  header can be overridden using my_hdr From:.
- When there is no real name, $realname is used for it.  Note that,
  when the default from header is used and $from defines a real
  name, it takes precedence over $realname.