Fix wrap-around month logic in calendar_tostringlist

[bterrier]

For year-wrapping calendar intervals like "12-2" (Dec-Feb), the else
branch matched months 2-12 instead of {12, 1, 2} -- the complement of
the intended set. Plants with winter blooming/fruiting periods (e.g.
Coffea arabica fruiting 12-2, Cymbidium cochleare blooming 12-1)
displayed the wrong months in their calendar widget.

Use OR instead of AND so the wrap-around branch covers months >= first
or <= second.

[emericg]

Yes that was wrong...
The plant database code is definitely not the most tested code (or even just used), so big thanks for having a look around :)