ssh_config: Match exec broken

[Klemens Nanni]

Just upgraded the latest snapshot

OpenBSD 6.3-beta (GENERIC.MP) #25: Fri Mar  2 14:41:23 MST 2018

The following ssh_config(5) snippet is now broken:

        Match exec "echo %n | grep -qxE 'some|nifty|regex'"
                Include some/config

        $ ssh some_host
        Unsupported Match attribute echo
        /home/kn/.ssh/config line 42: Bad Match condition

Reverting the following commit fixes this and I can connect again
regardless of matching:

        revision 1.124
        date: 2018/03/02 03:02:11;  author: djm;  state: Exp;  lines: +19 -8;  
commitid: nNRsCijZiGG6SUTT;
        Allow escaped quotes \" and \' in ssh_config and sshd_config quotes
        option strings. bz#1596 ok markus@