I expect this commit is to blame:

---------------------------- revision 1.21 date: 2009/11/13 13:50:26; author: per; state: Exp; lines: +4 -7 More sane signal arguments. Fixed common_draw so that it's actually possible to draw. The 'require gtk212' etc were not in effect, since there were no matching options in options.in. Fixed some random errors found while attempting to write an application. ----------------------------

The arguments might be more sane, but breaking compatibility with released versions on a stable branch really isn't...