Database code not postgresql compatible

The database code in node_breadcrumb is full of mysqlisms, which makes the module not work using postgresql.

This patch replaces the mysql-specific stuff with code that should work on both mysql and postgres.

The only feature that got lost in the process is the index for the key table, the index syntax seems very different between postgres and mysql. I'm sure there is a standard way of adding indexes in drupal if it's really needed.

I completely dropped the specification of a default charset, if the DB is created correctly it shouldn't be needed if I have understood things correctly.

In any case, this patch makes the thing work using postgres 8.2 and drupal 5.1 on Ubuntu Gutsy.