Support prefix tables

Hi,

I installed the Search Keywords module on my Drupal 4.7 website.
After installation, i got an error saying the database table 'rd_search_keywords_log' doesn't exist.
When checking my MySQL tables, i found that a table named 'search_keywords_log' was added, but all my other tables use the prefix 'rd_'. Of course this was easily solved by renaming the table to 'rd_search_keywords_log', but nevertheless i report this bug here to avoid this problems for other users.

I guess it is just a matter of adding {} brackets around the appropriate code that adds the database table, to support table prefixes.