Log Message:
Update heirloom-mailx to 12.5. From maintainer in PR pkg/49492.

Significant changes:
- MASTER_SITES now points at ${MASTER_SITE_DEBIAN:=pool/main/h/heirloom-mailx/}
- LICENSE filled out based on content of COPYING file in source
- addresses CVE-2004-2771 and CVE-2014-7844; address expansion disabled by
  default
- remove SSL2 related code to match state of OpenSSL