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LispMe Date/Time support

LispMe introduces four separate new data types (implemented as foreign types) for dealing with time-like data. These foreign types encapsulate the corresponding PalmOS types and therefore inherit their flaws:

PalmOS (until V4.0) has no idea of a timezone
Time values don't contain seconds

The four data types are

Date: Represents a date from 1904 to 2031 by year, month, and day. Dates are printed using the format selected in the system preferences.
Time: Contains only hour and minute components. Times are printed using the format selected in the system preferences.
Timestamp: A specific moment in time, accurate to 1 second, used for marking events, e.g. backup timestamp of a database. Timestamps are printed in a generic format yyyy-mm-dd-hh-mm-ss which allows sorting.
Ticks: The smallest measurable unit of time, starting with the last device reset and used mainly for performance measuring. A second contains (ticks-per-sec) (usually 100) ticks.

Please note the functions pick-date and pick-time which invoke the system dialogs for selecting dates and times.

Associated language elements

`current-ticks`	`current-ts`	`date+`	`date-day`	`date-diff`
`date-month`	`date-time`	`date-year`	`date?`	`day-of-week`
`make-date`	`make-time`	`make-ts`	`set-ticks`	`ticks-per-sec`
`ticks-since`	`ticks?`	`time-hour`	`time-minute`	`time?`
`ts->date`	`ts->number`	`ts->time`	`ts-second`	`ts?`