Change required GLib version in acinclude.m4

The g_strcmp0 function requires at least 2.16.
diff --git a/acinclude.m4 b/acinclude.m4
index ecf4b4b..9d3f6b2 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -108,8 +108,8 @@
 ])
 
 AC_DEFUN([AC_PATH_GLIB], [
-	PKG_CHECK_MODULES(GLIB, glib-2.0 >= 2.14, dummy=yes,
-				AC_MSG_ERROR(GLib library version 2.14 or later is required))
+	PKG_CHECK_MODULES(GLIB, glib-2.0 >= 2.16, dummy=yes,
+				AC_MSG_ERROR(GLib library version 2.16 or later is required))
 	AC_SUBST(GLIB_CFLAGS)
 	AC_SUBST(GLIB_LIBS)
 ])