Install the aclocal macros for use by Winelib apps.

diff --git a/Make.rules.in b/Make.rules.in
index ccd9585..f07b8d1 100644
--- a/Make.rules.in
+++ b/Make.rules.in
@@ -101,6 +101,7 @@
 exec_prefix     = @exec_prefix@
 bindir          = @bindir@
 libdir          = @libdir@
+datadir         = @datadir@
 infodir         = @infodir@
 mandir          = @mandir@
 sysconfdir      = @sysconfdir@