Always compute (possible) overflow in unsigned math. Avoids crash with

clang on startup. Bump revision.

devel/m4/Makefile

@@ -1,6 +1,7 @@
-# $NetBSD: Makefile,v 1.75 2017/08/25 05:28:53 adam Exp $
+# $NetBSD: Makefile,v 1.76 2018/09/25 20:21:51 joerg Exp $
 
 DISTNAME=	m4-1.4.18
+PKGREVISION=	1
 CATEGORIES=	devel
 MASTER_SITES=	${MASTER_SITE_GNU:=m4/}
 

devel/m4/distinfo

@@ -1,4 +1,4 @@
-$NetBSD: distinfo,v 1.43 2018/03/13 20:26:42 jmcneill Exp $
+$NetBSD: distinfo,v 1.44 2018/09/25 20:21:51 joerg Exp $
 
 SHA1 (m4-1.4.18.tar.gz) = 2f76f8105a45b05c8cfede97b3193cd88b31c657
 RMD160 (m4-1.4.18.tar.gz) = 16396a6ffbb2105cdd0a36c773b44d16854ed740
@@ -8,3 +8,4 @@ SHA1 (patch-isnan.c) = a960f35e5168bed47c5924e36bfb254dc1a44621
 SHA1 (patch-lib_getprogname.c) = 3a8e7c028342ef3a9f86839f1a5ae36571a65f12
 SHA1 (patch-lib_stdio.in.h) = 21557ea9d86dbeb36062df4e62cb71735b06480b
 SHA1 (patch-lib_vasnprintf.c) = 2bced6c121efc9bc5894174c7745ba89e8f53033
+SHA1 (patch-lib_xalloc-oversized.h) = 9e74adec2f43770d419f60d5c3e7bdea2424daa6

devel/m4/patches/patch-lib_xalloc-oversized.h

@@ -0,0 +1,16 @@
+$NetBSD: patch-lib_xalloc-oversized.h,v 1.1 2018/09/25 20:21:51 joerg Exp $
+
+--- lib/xalloc-oversized.h.orig	2018-08-19 18:13:08.426109176 +0000
++++ lib/xalloc-oversized.h
+@@ -35,11 +35,7 @@
+ #define __xalloc_oversized(n, s) \
+   ((size_t) (PTRDIFF_MAX < SIZE_MAX ? PTRDIFF_MAX : SIZE_MAX - 1) / (s) < (n))
+ 
+-#if PTRDIFF_MAX < SIZE_MAX
+-typedef ptrdiff_t __xalloc_count_type;
+-#else
+ typedef size_t __xalloc_count_type;
+-#endif
+ 
+ /* Return 1 if an array of N objects, each of size S, cannot exist
+    reliably due to size or ptrdiff_t arithmetic overflow.  S must be