Convert from timestamp to datetime. Datetime is consistent between mysql 4.0x and newer

versions and is faster for date/time computations. Modify object creation methods to specify
any time fields that were previously updated with timestamp properties.

tables/user_list.sql

@@ -3,13 +3,13 @@ use apidb;
 drop table if exists user_list;
 
 create table user_list (
-  stamp                   timestamp not null,
+  stamp                   datetime not null,
   userid                  int not null auto_increment,
   password                text not null,
   realname                text not null,
   email                   varchar(255) not null,
   created                 datetime not null,
-  inactivity_warn_stamp   timestamp not null, /* the time we warned the user */
+  inactivity_warn_stamp   datetime not null, /* the time we warned the user */
   inactivity_warned       enum('true','false') NOT NULL default 'false', /* if true, we warned the user */
   CVSrelease              text,
   unique key(userid),