changes to support logging

To support some of the logging changes I'm working on, I propose to add 
the following members to struct Port, unless anyone objects - these are 
all calculated in postmaster/postmaster.c:
 struct tm session_start; char * remote_host; char * remote_port;

Question: In setting these is it better to call strdup() or pstrdup() - 
the code comments aren't entirely clear on that.

Another thing:

I've noticed an inconsistency in calls to gettimeofday(): sometimes it 
is passed a struct tz (which is ignored) as the second argument, and 
sometimes NULL as the second argument. My understanding is that the 
second argument is basically useless anyway - on my Linux box man 
gettimeofday says this:
 The  use  of  the timezone struct is obsolete; the tz_dsttime field has never been used under Linux - it has not been
andwill not be supported by  libc or glibc.
 

I therefore propose to clean this up in the following places:
 backend/commands/vacuum.c backend/utils/adt/nabstime.c backend/postmaster/postmaster.c (3)

(I know it's a minor nit, but what the heck?)

cheers

andrew