It turns out we still support pre-auth compression on the client.
Therefore revert the previous two commits:

date: 2018/07/06 09:06:14;  author: sf;  commitid: yZVYKIRtUZWD9CmE;
 Rename COMP_DELAYED to COMP_ZLIB

 Only delayed compression is supported nowadays.

 ok markus@

date: 2018/07/06 09:05:01;  author: sf;  commitid: rEGuT5UgI9f6kddP;
 Remove leftovers from pre-authentication compression

 Support for this has been removed in 2016.
 COMP_DELAYED will be renamed in a later commit.

 ok markus@

OpenBSD-Commit-ID: cdfef526357e4e1483c86cf599491b2dafb77772