node_access rewrite breaks with FROM_UNIXTIME

The logic to break up a query in db_rewrite_query() has a minor bug in that it doesn't list _ as a valid extension to the FROM keyword, which means that the function FROM_UNIXTIME utterly breaks when node access is enabled. The attached patch adds a _ to the characters that can't follow the FROM keyword to make it a delimiter.

I took this patch against a version from CVS that I downloaded a couple of weeks ago. I doubt database.inc has changed enough that this patch won't work, but you never can tell. It should be extremely easy to apply manually if the patch fails, as it's a 1 character change in db_rewrite_sql() in database.inc