so far as used by the the __convert_time() function and the conversion
code in strftime().
- Also changed the algorithm used by strftime() to produce the week numbers
(the '%U' and '%W' format specifiers). The new method is much simpler
than the old one.
- Made the code that converts a 'time_t' value into the 'struct DateStamp',
as used by strftime() and utime(), into its own function. This also
fixes a bug in the code strftime() would use which was completely
unaware of the local time zone settings.