[gtkmm] Created tag 3.1.90

[Murray Cumming <murrayc src gnome org>]

The unsigned tag '3.1.90' was created.

Tagger: Murray Cumming <murrayc murrayc com>
Date: Wed Sep 14 10:10:10 2011 +0200

    3.1.90

Changes since the last tag '3.1.18':

Kjell Ahlstedt (1):
      TreeView: Make append_column_numeric_editable() work for [unsigned] short.

Murray Cumming (2):
      Widget::get_allocation(): Add the newer documentation from the C docs.
      3.1.90