Compatibility toolkits for Qdos and Minerva

These toolkits add the extended date functions found in SMSQ/E to Qdos
and Minerva, thus allowing programs that rely on this functionality to
run under those operating systems. Minerva already has the extended DATE
function built in therefore the toolkit comes in two versions; one with
DATE and the other without.

Note: Pre-JS QL ROMs do not allow keywords in the system ROM to be
overwritten by new definitions, so you cannot update the DATE function in
AH to JM ROMs using these toolkits! You could just as well use the Minerva
version in those cases, thus saving a few bytes.

The new keywords are as follows:

        yr% = YEAR%[(datestamp)]

        Returns the year 1961..2097. If no datestamp is supplied the
        current year is returned

        mn% = MONTH%[(datestamp)]

        Returns the month 1..12. If no datestamp is supplied the current
        month is returned

        md% = DAY%[(datestamp)]

        Returns the day of month 1..31. If no datestamp is supplied the
        current day of month is returned

        wd% = WEEKDAY%[(datestamp)] Returns the day of the week 0..6
        (= Sunday..Saturday). If no datestamp is supplied the current day
        of the week is returned.

        datestamp = DATE[(year, month, day, hour, minute, second)]

        Returns the number of seconds since January 1st 1961. If no
        parameters are supplied the current time in seconds is returned

The functional part of the code was pinched from the Minerva V1.98 sources,
© Laurence Reeves, which are released under the GNU GENERAL PUBLIC LICENSE,
Version 2, June 1991. The code was cobbled together by me, pjwitte. Any
bugs found will in all likelyhood be mine.

The sources are included.

April 25th 2019
pjwite at googlemail dot c0m