Fixed parameter type from guint to gint for set/get_indent_width

I think at some point this was changed in gsv to accomodate the
-1 default value, meaning to take the value from tab-width instead.
This was then not updated in the bindings, but now it is.

gtksourceview2.defs

@@ -802,14 +802,14 @@
   (c-name "gtk_source_view_set_indent_width")
   (return-type "none")
   (parameters
-    '("guint" "width")
+    '("gint" "width")
   )
 )
 
 (define-method get_indent_width
   (of-object "GtkSourceView")
   (c-name "gtk_source_view_get_indent_width")
-  (return-type "guint")
+  (return-type "gint")
 )
 
 (define-method set_tab_width