MFC r306075,r306109
- Microoptimize %p case.
- Implememt %u for GNU compatibility.
- Don't forget to advance buf for %w/%u.
- Fail with incomplete week (week 0) request and no such week in the
year.
- Fix yday formula when Sunday requested and the week started from Monday.
- Fail with impossible yday for incomplete week (week 0) and direct %w/%u
request.
- Shift yday/wday to the first day of the year, if incomplete week
(week 0) requested and no %w/%u used.
- For already non-standard %z extension implement GNU compatible formats:
+hh and -hh.
- Check for incorrect values for %z.
PR: 212983 (case 3 only)