Fix autotools m4 warning

.gitignore

@@ -25,4 +25,5 @@ ChangeLog
 xfce4-dev-tools-*.tar.bz2
 xdt-csource/*
 !xdt-csource/Makefile.am
-!xdt-csource/main.c
\ No newline at end of file
+!xdt-csource/main.c
+m4

Makefile.am

@@ -4,6 +4,8 @@
 # Written for Xfce by Benedikt Meurer <benny@xfce.org>.
 #
 
+ACLOCAL_AMFLAGS = -I m4 ${ACLOCAL_FLAGS}
+
 SUBDIRS = 								\
 	m4macros							\
 	scripts								\

autogen.sh

@@ -34,6 +34,8 @@ sed -e "s/@REVISION@/${revision}/g" < "configure.ac.in" > "configure.ac"
  automake --add-missing --copy --gnu &&
  autoconf) || exit 1
 
+test -d m4 || mkdir m4
+
 if test x"${NOCONFIGURE}" = x""; then
   (./configure --enable-maintainer-mode "$@" &&
    echo "Now type \"make\" to build.") || exit 1

configure.ac.in

@@ -27,6 +27,7 @@ dnl ***************************
 AC_INIT([xfce4-dev-tools], [xdt_version],
         [http://bugzilla.xfce.org/enter_bug.cgi?product=Xfce4-dev-tools])
 AC_COPYRIGHT([Copyright (c) 2002-2015 The Xfce development team. All rights reserved.])
+AC_CONFIG_MACRO_DIR([m4])
 
 dnl substitute version info
 AC_SUBST([VERSION_MAJOR], [xdt_version_major])