Add a regression test that (at least on some archs) catches the problem

fixed in  usr.bin/sort/fields.c rev. 1.18.

regress/usr.bin/Makefile

@@ -1,5 +1,5 @@
-#	$NetBSD: Makefile,v 1.6 2003/09/14 13:51:16 cjep Exp $
+#	$NetBSD: Makefile,v 1.7 2004/03/14 23:01:33 martin Exp $
 
-SUBDIR+= bzip2 grep m4 make rtld sort
+SUBDIR+= bzip2 grep m4 make rtld sort sort2
 
 .include <bsd.subdir.mk>

regress/usr.bin/sort2/Makefile

@@ -0,0 +1,8 @@
+#	$NetBSD: Makefile,v 1.1 2004/03/14 23:01:33 martin Exp $
+
+NOMAN=  	# defined
+
+regress:
+	@${HOST_SH} ${.CURDIR}/sort2regress
+
+.include <bsd.prog.mk>

regress/usr.bin/sort2/sort2regress

@@ -0,0 +1,18 @@
+#! /bin/sh
+
+INFILE=/tmp/sort-input.$$
+OUTFILE=/tmp/sort-output.$$
+
+trap "rm -f $INFFILE $OUTFILE; echo FAILED; exit 0" 1 ILL TRAP ABRT BUS SEGV
+
+printf "a b \na b\n" > $INFILE
+sort +3 $INFILE > $OUTFILE || { echo "FAILED"; rm -f $INFILE $OUTFILE; exit 0; }
+
+if cmp $INFILE $OUTFILE
+then
+	echo PASSED
+else
+	echo FAILED
+fi
+
+rm -f $INFILE $OUTFILE