Updated m4 to 1.4.16, and it now builds on Haiku without any patching needed.

sys-devel/m4/m4-1.4.16.bep

@@ -0,0 +1,29 @@
+DESCRIPTION="m4 - GNU macro processor" 
+HOMEPAGE="http://www.gnu.org/software/m4/" 
+SRC_URI="http://ftp.gnu.org/gnu/m4/m4-1.4.16.tar.gz"
+CHECKSUM_MD5="a5dfb4f2b7370e9d34293d23fd09b280"
+REVISION="1"
+STATUS_HAIKU="stable"
+DEPEND=""
+
+BUILD {
+	cd m4-1.4.16
+	./configure --prefix=`finddir B_COMMON_DIRECTORY` \
+		--enable-changeword \
+		--infodir=`finddir B_COMMON_DOCUMENTATION_DIRECTORY`/info \
+		--mandir=`finddir B_COMMON_DOCUMENTATION_DIRECTORY`/man
+	make
+}
+
+INSTALL {
+	cd m4-1.4.16
+	make install
+}
+
+TEST {
+	cd m4-1.4.16
+	make check
+}
+
+LICENSE="GNU GPL v3"
+COPYRIGHT="2000, 2005-2011 Free Software Foundation, Inc."