Raise the limit on the length of user names to the most utmp will
allow.  Based on a patch by Rik Brown.

diff -up krb5/src/appl/bsd/krshd.c krb5-1.6.1/src/appl/bsd/krshd.c
--- krb5/src/appl/bsd/krshd.c	2010-09-09 16:00:45.836924000 -0400
+++ krb5/src/appl/bsd/krshd.c	2010-09-09 17:19:16.205923995 -0400
@@ -195,6 +195,13 @@ Key_schedule v4_schedule;
 
 #define ARGSTR	"ek54ciD:S:M:AP:?L:w:"
 
+#ifdef HAVE_UTMP_H
+#include <utmp.h>
+#endif
+
+#ifndef UT_NAMESIZE	/* linux defines it directly in <utmp.h> */
+#define	UT_NAMESIZE	sizeof(((struct utmp *)0)->ut_name)
+#endif
 
 
 
@@ -486,7 +493,7 @@ char    username[32] = "LOGNAME=";
 #include <tmpdir.h>
 char tmpdir[64] = "TMPDIR=";
 #else
-char	username[20] = "USER=";
+char	username[UT_NAMESIZE + 6] = "USER=";
 #endif
 
 char	homedir[64] = "HOME=";
@@ -536,7 +543,7 @@ int maxlogs;
 #define NCARGS 1024
 #endif
 
-#define NMAX   16 
+#define NMAX   UT_NAMESIZE
 
 int pid;
 char locuser[NMAX+1];