(show_date): Use new fprintftime function rather than xanstrftime.
Correct comment: this function no longer handles a NULL format string.
* src/du.c: Likewise.
+ * NEWS: Mention this.
* tests/misc/date (subfmt-up1): Test the combination of the
to-upper-case modifier (^) and a conversion specifier that
"pr -D FORMAT" now accepts the same formats that "date +FORMAT" does.
+** Improved robustness
+
+ Date no longer needs to allocate virtual memory to do its job,
+ so it can no longer fail due to an out-of-memory condition,
+ no matter how large the result.
+
** Improved portability
hostid now prints exactly 8 hexadecimal digits, possibly with leading zeros,