Add support for dubious month/day dates

[peterdesmet]

11-12-2012 could be a little-endian date (11 december) or a middle-endian date (12 november) and is thus dubious.

Currently, the parser returns nothing for these dates, but the year can be unambiguously determined: 2012.

[cgendreau]

Do you think 0-0-2012 should return null or 2012?

[peterdesmet]

I would return 2012.

1-1-2012 is also a very common representation for 2012, but that one cannot be transformed to 2012.