[rygel] build: Bump vala requirement to 0.40

[Jens Georg <jensgeorg src gnome org>]

commit 5eacdaef5d6f0d3534e9fecb1047788e565055da
Author: Jens Georg <mail jensge org>
Date:   Mon Oct 22 16:56:45 2018 +0200

    build: Bump vala requirement to 0.40

 configure.ac | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/configure.ac b/configure.ac
index 9912de97..c7efd55d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -35,7 +35,7 @@ dnl Required versions of library packages
 dnl Not all of these are actually used, depending on the configure options.
 GLIB_REQUIRED=2.40.0
 LIBXML_REQUIRED=2.7
-VALA_REQUIRED=0.24.0
+VALA_REQUIRED=0.40.0
 VALADOC_REQUIRED=0.2
 GSSDP_REQUIRED=0.14.15
 GUPNP_REQUIRED=0.20.14