ChangeLog: Drop this optional file

Users who need a history can get it from the Git repository, and the
file is optional since at least 2006 [1].

[1]: https://gitweb.gentoo.org/proj/pms.git/commit/?id=81f522241733c87bcfca90b554082a2d0782cd8f

Manifest: Remove this file

Move to thin manifests [1,2] now that Gentoo supports them.

[1]: https://wiki.gentoo.org/wiki/Repository_format/package/Manifest#Thin_Manifest
[2]: https://wiki.gentoo.org/wiki/Repository_format/metadata/layout.conf#thin-manifests

dev-python/pyassuan: require Python 3.3 for socket.sendmsg() and .recvmsg().

Add dev-python/pyassuan package.