defines strftime(), but can also define wcsftime(); add optional
test package; speed up %Y handling.
* libc/time/wcsftime.c: New file, defining wcsftime() (albeit
indirectly by including strftime.c) and its documentation.
* libc/time/time.tex: Enhance tm_isdst explanation, change strftime
description to match modified description in strftime.c
* libc/time/Makefile.am: Add wcsftime.c and wcsftime.def. Add a rule
so that wcsftime.o gets rebuilt when strftime changes.
* libc/time/Makefile.in: Regenerate.
* libc/include/wchar.h (wcsftime): Declare.
* libc/time/time.tex: Improve the documentation.
* libc/time/strftime.c: Improve the documentation.
(iso_year_adjust): New helper function.
(strftime): Simplify '%E' and '%O'. Change '%c' to use
recursion. Fix '%C', '%y', and '%Y' to deal with years with more
than 4 characters. Combine '%d' and '%e'. Implement '%D', '%F',
'%g', '%G', '%n', '%R', '%t', '%T', '%u', '%V', '%X', and '%z'.
Avoid core dumps on valid inputs (maxsize == 0, or
tim_p->tm_isdst > 1).
Corinna Vinschen
Jeff Johnston
Christopher Faylor