Remove support for old version (per-8.4) of postgresql

The _fix_timezone sub had a workaround for a bug in postgresql's
handling of pre-1901 an post-2038 dates. This is no longer needed.
The bug was fixed in pg 8.4. The fix is to remove the work around
and the corresponding test. As we get closer to 2038 this will
become more apparent.

lib/DateTime/Format/Pg.pm

@@ -340,26 +340,6 @@ sub _fix_timezone {
     $args{'parsed'}->{'time_zone'} = $param{'_force_tz'};
   }
 
-  elsif(!defined($args{'parsed'}->{'time_zone'})) {
-    # For very early and late dates, PostgreSQL always returns times in
-    # UTC and does not tell us that it did so.
-    #
-    if ( $args{'parsed'}->{'year'} < 1901
-    || ( $args{'parsed'}->{'year'} == 1901 && ($args{'parsed'}->{'month'} < 12 || $args{'parsed'}->{'day'} < 14) )
-    ||   $args{'parsed'}->{'year'} > 2038
-    || ( $args{'parsed'}->{'year'} == 2038 && ($args{'parsed'}->{'month'} > 01 || $args{'parsed'}->{'day'} > 18) )
-    ) {
-    $args{'parsed'}->{'time_zone'} = DateTime::TimeZone::UTC->new();
-    }
-
-    # DT->new() does not like undef time_zone params, which are generated
-    # by the regexps
-    #
-    else {
-      delete $args{'parsed'}->{'time_zone'};
-    }
-  }
-
   # Numerical time zone
   #