Create a local m4 subdirectory
--- a/Makefile.am
+++ b/Makefile.am
@@ -12,6 +12,8 @@
 # require automake 1.5
 AUTOMAKE_OPTIONS = 1.5
 
+ACLOCAL_AMFLAGS = -I m4
+
 EXTRA_DIST =                    \
         HISTORY                 \
         config.h.win32          \
