correct exit values when unveil/pledge do not succeed on mesg(1)

[Ricardo Mestre]

Hi,

This one was my fault, mesg(1) should only return 1 when we disallow
messages. When we want to exit if an error has occurred it must be >1
instead. Additionally the err(3) for the pledge case must be changed.

OK?

Index: mesg.c
===================================================================
RCS file: /cvs/src/usr.bin/mesg/mesg.c,v
retrieving revision 1.13
diff -u -p -u -r1.13 mesg.c
--- mesg.c      3 Aug 2018 06:57:34 -0000       1.13
+++ mesg.c      10 Aug 2018 09:55:34 -0000
@@ -65,9 +65,9 @@ main(int argc, char *argv[])
                err(2, "ttyname");
 
        if (unveil(tty, "rw") == -1)
-               err(1, "unveil");
+               err(2, "unveil");
        if (pledge("stdio rpath fattr", NULL) == -1)
-               err(1, "unveil");
+               err(2, "pledge");
 
        if (stat(tty, &sb) < 0)
                err(2, "%s", tty);