Add AC_CONFIG_MACRO_DIR() to configure.ac as suggested by libtoolize

Also set ACLOCAL_AMFLAGS in the top-level Makefile.am and update
the .gitignore file in the m4macros directory. This fixes the build
from a fresh checkout for me. Please revert if it causes problems.

Makefile.am

@@ -1,5 +1,7 @@
 ## Process this file with automake to produce Makefile.in
 
+ACLOCAL_AMFLAGS = -I m4macros
+
 SUBDIRS = \
 	m4macros	\
 	tools		\

configure.ac

@@ -68,6 +68,7 @@ AC_INIT([GIMP], [gimp_version],
         [gimp])
 
 AC_CONFIG_SRCDIR([app/core/gimp.c])
+AC_CONFIG_MACRO_DIR([m4macros])
 
 AM_INIT_AUTOMAKE(no-define dist-bzip2)
 AM_CONFIG_HEADER(config.h)

m4macros/.gitignore

@@ -1,2 +1,9 @@
-/Makefile
-/Makefile.in
+Makefile
+Makefile.in
+gtk-doc.m4
+intltool.m4
+libtool.m4
+lt~obsolete.m4
+ltoptions.m4
+ltsugar.m4
+ltversion.m4