crypt'd version of the password in the database, and check against
that.  (This is silly, because we're also keeping the plaintext
version there, but I have plans...)  Stop passing the plaintext
password around as a cookie; instead, we have a cookie that references
a record in a new database table, logincookies.

IMPORTANT: if updating from an older version of Bugzilla, you must run
the following commands to keep things working:

 ./makelogincookiestable.sh
 echo "alter table profiles add column cryptpassword varchar(64);" | mysql bugs
 echo "update profiles set cryptpassword = encrypt(password,substring(rand(),3, 4));" | mysql bugs