Make it possible to have multiple tags on a configuration block.

[kurganme]

This patch allows for multiple tags on a configuration block.
For instance, with this configuration:

Host test-host
  Tag change-hostname change-port-and-user
  Tag jump-to-mybox

Match tagged change-hostname
  Hostname new-hostname

Match tagged change-port-and-user
  Port 12345
  Tag change-user

Match tagged change-user
  User bilbo

Match tagged jump-to-mybox
  ProxyJump mybox

Match tagged nocheck
  StrictHostKeyChecking false
  UserKnownHostsFile /dev/null

Match tagged frodo-identity
  IdentityFile ~/.ssh/id_ed25519_frodo

the following parameters can be obtained:

gandalf@mybox $ ssh -P nocheck -P frodo-identity test-host -G |
> grep -E "^(user|hostname|port|stricthostkeychecking|identityfile|`
>         `userknownhostsfile|tag|proxyjump) "
user bilbo
hostname new-hostname
port 12345
stricthostkeychecking false
identityfile ~/.ssh/id_ed25519_frodo
userknownhostsfile /dev/null
tag nocheck
tag frodo-identity
tag change-hostname
tag change-port-and-user
tag jump-to-mybox
tag change-user
proxyjump mybox
gandalf@mybox $