Tweak IFS handling in portcheck(1), based on input from Andres Perera for

another tool.

infrastructure/bin/portcheck

@@ -1,6 +1,6 @@
 #!/bin/ksh
 #
-# $OpenBSD: portcheck,v 1.74 2014/05/06 11:00:55 zhuk Exp $
+# $OpenBSD: portcheck,v 1.75 2014/05/07 21:57:00 zhuk Exp $
 # Copyright (c) 2013 Vadim Zhukov
 # 
 # Permission to use, copy, modify, and distribute this software for any
@@ -1492,9 +1492,7 @@ check_makefile() {
 	# do not unset mkvars, having empty element(-s) is fine
 	unset revs[0]
 	local tab="$(print '\t')"
-	IFS=
-	while read -r l; do ((++lnum))
-		unset IFS
+	while IFS= read -r l; do ((++lnum))
 		set -A t -- $l
 		duprevfound=false
 
@@ -1543,9 +1541,7 @@ check_makefile() {
 			done
 			mkvars[${#mkvars[@]}]=$var
 		fi
-		IFS=
 	done <"$F"
-	unset IFS
 }
 
 # Checks made: