Not all parsedate terms work

[humdinger]

This is hrev33939.

In ​parsedate.cpp are all kinds of terms defined. Not all seem to work 100%. (I'm using the Find panel, BTW, so I rely on it to produce the right query formulas. )

• Absolute dates don't work, e.g. "23.06.2009" or "06/23/2009". Those would be convenient.

• "Monday" works, but "October" doesn't. Here you have to qualify "this October". I think, "this" should be implied if nothing else is given (like "last" for the one last year. BTW: does "next" make any sense at all? Will it find files from the future? (Note to self, write down the lottery numbers next weekend.))

• Contrary to the above, when not searching for named dates like Monday or October (TYPE_WEEKDAY and TYPE_MONTHS) but TYPE_UNIT like days, weeks, months, years, defaulting to "last" makes sense. Right now a query after "last 2 months" works, but after "2 months" doesn't. The "last" isn't really intuitive, and what else could be meant when searching for something in a 2-months timeframe?

Mind you: that's only for the plural! When dealing with the singular, day, week, month, year, it should default to "this" as explicitly stating "last" means the day, week, month, year before the current one.

See also #4181 which may be related.