dblog_watchdog() should truncate data going into varchar fields

Insert queries on the watchdog table fail for entries with data that exceeds the varchar lengths on particular fields - failing to insert the data into the table, as would be expected.

For example visiting the following url, and then clicking on a link will generate an error when the referer varchar limit is exceeded:
http://www.example.com/drupal/node?param001=1&param002=2&param003=3&para...

Amusingly it will then try and record another watchdog entry for that failed error, but it will also fail.

The following errors were generated in the error_log file:

PHP Warning:  pg_query() [<a href='function.pg-query'>function.pg-query</a>]: Query failed: ERROR:  value too long for type character varying(128) in /drupal/includes/database.pgsql.inc on line 155

PHP Warning:  ERROR:  value too long for type character varying(128)\nquery: INSERT INTO watchdog\n    (uid, type, message, variables, severity, link, location, referer, hostname, timestamp)\n    VALUES\n    (79580, &#039;php&#039;, &#039;%message in %file on line %line.&#039;, &#039;a:4:{s:6:&quot;%error&quot;;s:7:&quot;warning&quot;;s:8:&quot;%message&quot;;s:132:&quot;pg_query() [&lt;a href=&#039;&#039;function.pg-query&#039;&#039;&gt;function.pg-query&lt;/a&gt;]: Query failed: ERROR:  value too long for type character varying(128)&quot;;s:5:&quot;%file&quot;;s:78:&quot;/drupal/includes/database.pgsql.inc&quot;;s:5:&quot;%line&quot;;i:155;}&#039;, 3, &#039;&#039;, &#039;http://dev.example.com/drupal/www.example.com/www/node&#039;, &#039;http://dev.example.com/drupal/www.example.com/www/index.php?param001=1&amp;param002=1&amp;param003=3&amp;param004=4&amp;param005=5&amp;param006=6&amp;param007=7&#039;, &#039;192.168.100.179&#039;, 1202361484) in /drupal/includes/database.pgsql.inc on line 176

The attached patch truncates the data to fit the fields. Alternatively one could change the varchars to text, or increase their lengths.