Add a devctl_process_running man page.

Document devctl_safe_quote_sb

This routine centralizes the knowledge needed for properly quoting
'value' in all key="value" items that appear in devctl messages.

Document quoting requirements for the devctl protocol

Belatedly document the quoting requirements for the devctl protocol. I
thought they'd been previously documented.

Also, while I'm here, make igor happy.

Add devctl_notify(9) man page

Document the calls to send messages to userland via devctl.
devctl_notify will create a message for the specified system,
subsystem and type, optionally adding additional information.