Properly fix a bug where, under certain conditions, annot was grabbing non-annot overlays such as the ones created by show-paren-mode thereby attaching annot-defined overlay properties outside of annot's disposal. This change introduces the annot-overlays-in wrapper function and annot-available-types const variable.

git-svn-id: http://annot.googlecode.com/svn/trunk@49 79ab45cb-065a-afc0-5cac-f6f03ead9b9a