Instead of setting up the default keys by building the key struct

directly with a helper function in the cmd_entry, include a table of
bind-key commands and pass them through the command parser and a
temporary cmd_q.

As well as being smaller, this will allow default bindings to be command
sequences which will probably be needed soon.

cmd-attach-session.c

@@ -37,7 +37,6 @@ const struct cmd_entry cmd_attach_session_entry = {
 	"c:drt:", 0, 0,
 	"[-dr] [-c working-directory] " CMD_TARGET_SESSION_USAGE,
 	CMD_CANTNEST|CMD_STARTSERVER,
-	NULL,
 	cmd_attach_session_exec
 };