- Remove useless includes

- Add WARNS?= 6 to Makefile

Submitted by:	Liam J. Foy <liamfoy@gmail.com>
Approved by:	grehan (mentor)

usr.bin/logname/Makefile

@@ -2,5 +2,6 @@
 # $FreeBSD$
 
 PROG=	logname
+WARNS?= 6
 
 .include <bsd.prog.mk>

usr.bin/logname/logname.c

@@ -44,11 +44,9 @@ static const char sccsid[] = "@(#)logname.c	8.2 (Berkeley) 4/3/94";
 __FBSDID("$FreeBSD$");
 
 #include <err.h>
-#include <errno.h>
 #include <unistd.h>
 #include <stdio.h>
 #include <stdlib.h>
-#include <string.h>
 
 void usage(void);