Add extra include file for aix to find endian information.

 including arguments allowed.

 having to modify the system-wide library database.

Define constants to allow day of week decoding.
Add new datetime and timespan routines.

Remove older date and time code (retain NEW_DATE_CODE and NEW_TIME_CODE).
Use common encoder for date and time.
Fix datetime +/- timespan math bug.

 This is compatible with abstime formats.

 #defines.

Add timezone info to abstime2tm().

 This allows use of the DateStyle session variable.

 This matches the behavior of the original formatting for abstime.
Repair datetime + timespan date arithmetic for year boundaries.
 From patch submitted by Dave Skinner.

 datetime +/- timespan. Only manifested when date is at end of month
 and time pushes the date into the next month.

 added for keyword=value options.

 the problem only manifests itself when adding years/months and hours
 when the hours:minutes:seconds pushes over midnight.
Fix interpretation of times with explicit timezone when the timezone is
 in daylight savings time and is not the default timezone.
Allow interpretation of explicit timezone when it is specified as two words:
 <standard time> DST". For example, "MET DST" (Middle European Time Daylight
 Savings Time). This syntax is found in the zic package on Linux boxes at least.

varno/varattno.

Update the update date.