YEARFRAC again

Hi,

We already found out that OOo calculation for YEARFRAC's ACTUAL mode in
some corner cases is wrong, so I'll remove that TODO. However, there's
another TODO for YEARFRAC

| TODO: Applications should probably implement the other actual/actual
| systems; we need to allocate “basis” numbers to them that everyone
| agrees on.

I don't think we should define other systems there, for
interoperability's sake. I'll remove that as well if noone disagrees.

  Eike

-- 
Automatic string conversions considered dangerous. They are the GOTO statements
of spreadsheets.  --Robert Weir on the OpenDocument formula subcommittee's list.