- Changed some "default NULL"s to "default NOT NULL"s as this only works on
  recent MySQL versions.  I included the diffs for review.

update.php:
-  update_sql("CREATE TABLE search_index (word varchar(50) default NULL, lno in
+  update_sql("CREATE TABLE search_index (word varchar(50) default NOT NULL, ln

database.mysql:
-  word varchar(50) default NULL,
-  lno int(10) unsigned default NULL,
-  type varchar(16) default NULL,
-  count int(10) unsigned default NULL,
+ word varchar(50) NOT NULL,
+ lno int(10) unsigned NOT NULL,
+ type varchar(16) default NULL,
+ count int(10) unsigned default NULL,