[gegl] depend on babl 0.1.40 or newer

[Øyvind Kolås <ok src gnome org>]

commit 60f2c0320a7f073a5bccf0d2a18ed88a7184b820
Author: Øyvind Kolås <pippin gimp org>
Date:   Wed Jan 17 16:01:46 2018 +0100

    depend on babl 0.1.40 or newer

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 292e7f2..41b45ab 100644
--- a/configure.ac
+++ b/configure.ac
@@ -37,7 +37,7 @@ m4_define([gegl_stable],
 m4_define([gimp_full_name], [Generic Graphical Library])
 
 # required versions of external libraries
-m4_define([babl_required_version], [0.1.39])
+m4_define([babl_required_version], [0.1.40])
 m4_define([cairo_required_version], [1.12.2])
 m4_define([exiv2_required_version], [0.25])
 m4_define([gdk_pixbuf_required_version], [2.32.0])