Added a more configurable error reporting interface to DB.
Also added some more tests, and moved the DB tests to pear/DB/tests.
#Usage example that prints and exits on every error:
#$dbh = DB::connect($dsn);
#$dbh->setErrorHandling(PEAR_ERROR_DIE);
#
#Example with plain callback function:
#$dbh->setErrorHandling(PEAR_ERROR_CALLBACK, "errorHandler");
#
#Example with object callback function:
#$dbh->setErrorHandling(PEAR_ERROR_CALLBACK, array($obj, "errorHandler"));
#
#Handler functions/methods are called with the error object as a parameter.
#
