Convert sh-like conditional style to gmake's one.

gmake-3.82 dislike it.

mail/ifile/distinfo

@@ -1,6 +1,7 @@
-$NetBSD: distinfo,v 1.7 2005/02/24 09:59:23 agc Exp $
+$NetBSD: distinfo,v 1.8 2010/10/03 12:47:20 obache Exp $
 
 SHA1 (ifile-1.3.4/ifile-1.3.4.tar.gz) = c8ef75cfe8f25af65b3384e016b7fd2d324346b0
 RMD160 (ifile-1.3.4/ifile-1.3.4.tar.gz) = ac13f9b8ba99319be61764ffb9492cc9405b3ea7
 Size (ifile-1.3.4/ifile-1.3.4.tar.gz) = 187742 bytes
 SHA1 (patch-aa) = c61f441f9bcae546fcebe351be02cad9f1e3b00a
+SHA1 (patch-ad) = 6b92eec1416a40cc692ff58915f8ebf133160f6a

mail/ifile/patches/patch-ad

@@ -0,0 +1,19 @@
+$NetBSD: patch-ad,v 1.1 2010/10/03 12:47:20 obache Exp $
+
+--- Makefile.in.orig	2004-11-19 22:51:24.000000000 +0000
++++ Makefile.in
+@@ -54,8 +54,12 @@ bindir = @bindir@
+ mandir = @mandir@
+ 
+ # Installation locations
+-if [ ! $bindir ] ; then bindir = $(exec_prefix)/bin; fi
+-if [ ! $mandir ] ; then mandir = $(prefix)/man; fi
++ifeq ($(strip $(bindir)),)
++  bindir = $(exec_prefix)/bin
++endif
++ifeq ($(strip $(mandir)),)
++  mandir = $(prefix)/man
++endif
+ 
+ #### This is just a test---feel free to delete ###
+ printdirs: