[libxml2] Add missing file xmlwin32version.h.in to EXTRA_DIST

[Nick Wellnhofer <nwellnhof src gnome org>]

commit 7d4060d252354a8d650a3c50256fe3679a40691d
Author: Markus Rickert <rickert fortiss org>
Date:   Sun May 16 18:00:21 2021 +0200

    Add missing file xmlwin32version.h.in to EXTRA_DIST

 include/libxml/Makefile.am | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/include/libxml/Makefile.am b/include/libxml/Makefile.am
index cf9297aa..328c1800 100644
--- a/include/libxml/Makefile.am
+++ b/include/libxml/Makefile.am
@@ -51,4 +51,4 @@ xmlinc_HEADERS = \
                xmlsave.h \
                schematron.h
 
-EXTRA_DIST = xmlversion.h.in
+EXTRA_DIST = xmlversion.h.in xmlwin32version.h.in