gWidgetsRGtk2

Changes for version 0.0-30
--------------------------

* Changed definition of basic widgets to use ANY instead of a class
  union that container either guiWidget, gWidgetRGtk2 or
  RGtkObject. The new is feature of 2.7.0 was messing this up. Should
  fix this.

* new function as.gWidgetsRGtk2 for coercing an RGtkObject object into
  a gWidgetsRGtk2 object 

* added anchor argument to ggroup

* fixed glayout so that visible assignment is not needed. The widget
  now resizes dynamically when asked. Added expand argument, and
  anchor argument.

* fixed handler for gradio.

* added handlers blockHandler, unblockHandler. These may be useful
  when updating a widget's values causes a handler to be called

* gwindow. Add menubars, toolbars, and statusbars directly to the top
  level gwindow object

* gtext: added addHandlerKeystroke. The value h$keystroke contains the
  key
