Fix wording, from Paul de Weerd

Rephrase the target section.

Document the persist option.

Only close the fd if its actually open.

Slightly clearer error message on !permit.

Do proper return value checking around close.

Do seteuid check for clearer error message.

Allow vias to do config file checking without specifying a file.

Use waitpid instead of wait, since it's better practice.

Change ruid back to original value before calling authuser. TIOCCHKVERAUTH comares the ruids, which made doas and vias logout one another.

TOWNER -> TAS

Remove all OpenBSD headers to distantiate this code from the project. Add a README that warns of the risks.

Import vias