[gnome-calendar] build: Require GTK+ 3.19.1

[Andreas Henriksson <ah src gnome org>]

commit 724db9973fe0fa9c65a4311dc4aa245e20b21e10
Author: Andreas Henriksson <andreas henriksson endian se>
Date:   Fri Mar 25 08:13:16 2016 +0100

    build: Require GTK+ 3.19.1
    
    Code already uses new API gtk_widget_class_set_css_name which
    was introduced in that version.

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 7589a99..924faa8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -80,7 +80,7 @@ MAINTAINER_COMPILER_FLAGS=${MAINTAINER_COMPILER_FLAGS#*  }
 AC_SUBST(MAINTAINER_COMPILER_FLAGS)
 
 GLIB_MIN_VERSION=2.43.4
-GTK_MIN_VERSION=3.15.4
+GTK_MIN_VERSION=3.19.1
 ECAL_REQUIRED=3.13.90
 EDATASERVER_REQUIRED=3.17.1
 EDATASERVERUI_REQUIRED=3.17.1