[valadoc] build: Add missing condition for valac <= 0.23.1 driver builds

[Rico Tzschichholz <ricotz src gnome org>]

commit 42cfa796f254aeb6cafc9f260dcb07ca8db7bf82
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Fri Jan 17 18:24:25 2014 +0100

    build: Add missing condition for valac <= 0.23.1 driver builds

 src/driver/Makefile.am |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/src/driver/Makefile.am b/src/driver/Makefile.am
index ea90014..440d0c4 100644
--- a/src/driver/Makefile.am
+++ b/src/driver/Makefile.am
@@ -28,6 +28,10 @@ if HAVE_LIBVALA_0_22_X
 DRIVER_0_22_X_DIR = 0.22.x
 endif
 
+if HAVE_LIBVALA_0_23_1
+DRIVER_0_24_X_DIR = 0.24.x
+endif
+
 if HAVE_LIBVALA_0_24_X
 DRIVER_0_24_X_DIR = 0.24.x
 endif