remove G_DEFINE_BOXED_TYPE() use

was glib-2.26+ only argh, thanks Jake

ChangeLog

@@ -7,6 +7,7 @@
 - add "nocache" operation flag, set for sequential load (thanks Diuming)
 - fix a crash in the tiff reader for huge values of RowsPerStrip (thanks
   Nicolas)
+- remove use of G_DEFINE_BOXED_TYPE() to help compat (thanks Jake)
 
 19/4/12 started 7.28.5
 - ifthenelse blend mode was broken

libvips/iofuncs/type.c

@@ -101,10 +101,29 @@ vips_thing_get_i( VipsThing *thing )
 	return( thing->i );
 }
 
+/*
+ * glib-2.26+ only 
+ 
 G_DEFINE_BOXED_TYPE( VipsThing, vips_thing,
 	(GBoxedCopyFunc) vips_thing_copy, 
 	(GBoxedFreeFunc) vips_thing_free );
 
+ */
+
+GType
+vips_thing_get_type( void )
+{
+	static GType type = 0;
+
+	if( !type ) {
+		type = g_boxed_type_register_static( "VipsThing",
+			(GBoxedCopyFunc) vips_thing_copy, 
+			(GBoxedFreeFunc) vips_thing_free );
+	}
+
+	return( type );
+}
+
 /**
  * SECTION: VipsArea
  * @short_description: an area of memory