Require glib >= 2.16 for the gobject option

configure.ac

@@ -87,7 +87,7 @@ if $have_gthread; then
 fi
 AM_CONDITIONAL(HAVE_GTHREAD, $have_gthread)
 
-PKG_CHECK_MODULES(GOBJECT, gobject-2.0, have_gobject=true, have_gobject=false)
+PKG_CHECK_MODULES(GOBJECT, gobject-2.0 glib-2.0 >= 2.16, have_gobject=true, have_gobject=false)
 if $have_gobject; then
 	AC_DEFINE(HAVE_GOBJECT, 1, [Have gobject2 library])
 	GLIB_MKENUMS=`$PKG_CONFIG --variable=glib_mkenums glib-2.0`