The previous port to the draw function was a tiny bit incomplete. This
patch should fix the remaining issues and remove unused variables.

The function reverses the transform that GTK does before emitting a draw
event. So we can use it in "old" widgets to revert the coordinate system
properly.

This mostly goes to keep consistency with the changes to GtkSizeRequest
in the last patch, as GtkCellSizeRequest requires GtkCellRenderer and
GtkCellRenderer implements GtkCellSizeRequest there's no use in keeping
them separate.

This patch renames the functions:
gtk_cell_size_request_get_request_mode()
  => gtk_cell_renderer_get_request_mode()
gtk_cell_size_request_get_width()
  => gtk_cell_renderer_get_preferred_width()
gtk_cell_size_request_get_height()
  => gtk_cell_renderer_get_preferred_height()
gtk_cell_size_request_get_size()
  => gtk_cell_renderer_get_preferred_size()
gtk_cell_size_request_get_width_for_height()
  => gtk_cell_renderer_get_preferred_width_for_height()
gtk_cell_size_request_get_height_for_width()
  => gtk_cell_renderer_get_preferred_height_for_width()
... and moves the corresponding vfuncs to GtkCellRenderer.

The patch also renames the implementations of these functions in cell
renderers to include the word "preferrred".

It doesn't make sense to keep them separate as GtkSizeRequest requires a
GtkWidget and GtkWidget implements GtkSizeRequest, so you can never have
one without the other.
It also makes the code a lot easier because no casts are required when
calling functions.

Also, the names would translate to gtk_widget_get_width() and people
agreed that this would be a too generic name, so a "preferred" was added
to the names.

So this patch moves the functions:
gtk_size_request_get_request_mode() => gtk_widget_get_request_mode()
gtk_size_request_get_width() => gtk_widget_get_preferred_width()
gtk_size_request_get_height() => gtk_widget_get_preferred_height()
gtk_size_request_get_size() => gtk_widget_get_preferred_size()
gtk_size_request_get_width_for_height() =>
  gtk_widget_get_preferred_width_for_height()
gtk_size_request_get_height_for_width() =>
  gtk_widget_get_preferred_height_for_width()
... and moves the corresponding vfuncs to the GtkWidgetClass.

The patch also renames the implementations of the vfuncs in widgets to
include the word "preferrred".

Following the mailing list discussion, require that the widget does not
have a pending size_allocate when calling the draw function.

http://mail.gnome.org/archives/gtk-devel-list/2010-September/msg00214.html
and the associated thread explain this in more detail.

And here's the final patch that all the previous patches were about.

The next commit will rename gtk_cell_renderer_render_cairo() to
gtk_cell_renderer_render() again

and rename gtk_cairo_draw_insertion_cursor() to
gtk_draw_insertion_cursor().

Large patch, but just renaming.
Indentation should still mostly be correct because I took care of
keeping the indentation for this function name.

gtk_widget_send_expose() now calls the draw function.

Also, move the documentation to its replacement
gtk_widget_propagate_draw().