net-mail/poppassd_ceti: bump 1.8.7, EAPI=7

net-mail/poppassd_ceti: bump 1.8.7, EAPI=7

In addition to 1.8.7 changes from upstream, the changes
compared to 1.8.5-r2 include:
  - Change to EAPI=7.
  - LICENSE=GPL-2+ (Although strictly speaking the "or later version"
    terminology was only added upstream after the 1.8.7 tarball was cut.)
  - Drop the xinetd RDEPEND, and document it (and the sudo
    alternative) using readme.gentoo-r1.eclass

Bug: https://bugs.gentoo.org/696252
Signed-off-by: Matthew Ogilvie <mmogilvi+gnto@zoho.com>
Signed-off-by: Michał Górny <mgorny@gentoo.org>