Comment 8 for bug 197010

Alternately, if a 2.12.1 update is not acceptable for whatever reason, I believe you should be able to isolate the patch fairly easily and include it in your package. I believe this is it:
http://svn.gnome.org/viewvc/gtkmm?view=revision&revision=914

Also, just to add a bit of explanation for all of the changes between 2.12.0 and 2.12.1:
a) gtkmm includes pre-built documentation so that the user isn't required to have doxygen isntalled to get the API documentation
b) gtkmm is largely auto-generated from the GTK+ sources, so a very small change to one of the macros used to auto-generate the code is likely to result in lots of small changes in many files.