Add the "windows" directory to EXTRA_DIST.
diff --git a/Makefile.am b/Makefile.am
index 8342ebb..507fe33 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -26,6 +26,7 @@
 	Doxyfile.in \
 	extra \
 	doc \
+	windows \
 	COPYING.GPLv2 \
 	COPYING.GPLv3 \
 	COPYING.LGPLv2.1