Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Drop the include for <stdint.h>, it was only needed when this was
using __DECONST() for something, and that reference has been removed.

Noticed by: Helge Oldach
MFC after: 13 days

Handle a 'const' parameter without using __DECONST().

MFC after: 14 days

Restructure the time processing routines, mainly to fix up the
"will trim at" message printed when the user requests '-v'. The
previous code would often print the wrong time, such as:
On Sept 22, run: newsyslog -nv /var/log/wtmp
And see: will trim at Mon Sep 1 05:00:00 2003
correct msg: will trim at Wed Oct 1 05:00:00 2003

MFC after: 20 days

Correct the calculation of "a leap year" in parseDWM. The calculation
would only match a leap year every 400 years. The parseDWM code first
showed up in April 2000, so the first time this bug would cause any
confusion is in Feb 2004.

MFC after: 18 days

Move the parse8601 and parseDWM routines into a new ptime.c file. The
only code-change is to add a "next_time" parameter to both routines (and
that is not used yet). A later update will make "next_time" more useful.

MFC after: 20 days