Require automake-1.16.3 or later

See https://gitlab.gnome.org/GNOME/libxml2/-/commit/df003c0aea767904c44de1bf420dc2a721347ad3

Require automake-1.16.3 or later
e906ad7a0b43 · Nick Wellnhofer · f228393fe2ef · e906ad7a
Commit e906ad7a0b43 authored 2 years ago by Nick Wellnhofer
--- a/configure.ac
+++ b/configure.ac
@@ -67,7 +67,7 @@
 AC_SUBST(LIBEXSLT_VERSION_NUMBER)
 AC_SUBST(LIBEXSLT_VERSION_EXTRA)

-AM_INIT_AUTOMAKE([1.15 foreign no-dist-gzip dist-xz])
+AM_INIT_AUTOMAKE([1.16.3 foreign no-dist-gzip dist-xz])
 AM_MAINTAINER_MODE([enable])
 AM_SILENT_RULES([yes])