Trying to do hooks generically is way too complicated and unreliable and

confusing, particularly trying to automatically figure out what target
hooks should be using. So simplify it:

- drop before hooks entirely, they don't seem to be very useful;

- commands with special requirements now fire their own after hook (for
  example, if they change session or window, or if they have -t and -s
  and need to choose which one the hook uses as current target);

- commands with no special requirements can have the CMD_AFTERHOOK flag
  added and they will use the -t state.

At the moment new-session, new-window, split-window fire their own hook,
and display-message uses the flag. The remaining commands still need to
be looked at.

hooks.c

@@ -196,6 +196,9 @@ hooks_wait(struct hooks *hooks, struct cmd_q *cmdq, struct cmd_find_state *fs,
 	va_list		 ap;
 	char		*name;
 
+	if (cmdq->flags & CMD_Q_NOHOOKS)
+		return (-1);
+
 	va_start(ap, fmt);
 	xvasprintf(&name, fmt, ap);
 	va_end(ap);