[Orgmode] org-bbdb: anniversaries with unknown years

[Christoph Groth]

Hello,

I'd like to keep birthdays and similar dates in bbdb and have them shown
in my org mode agenda views.  Often, however, I do not know the year of
an anniversary, and in the case of my acquaintances the year of a
personal anniversary is often not meaningful (e.g. name days, popular in
some countries).

The solution that came to my mind was to update org-bbdg.el to also
accept dates in the format MM-DD.  org-bbdb-anniv-extract-date would
then substitute nil for unknown years.  The remaining code would make
sure that "unknown" is substituted for unknown `years'.

That solution seems fine, however it would break compatibility with the
old format of org-bbdb-anniversary-format-alist, as this assumes that a
numerical value of `years' is always defined.

Before writing a patch, I would like to ask for opinions on this.

Cheers
Christoph