[Sync-En] pdo: revert constant types to int and document the getAttribute() bool change

[lacatoire]

Translation of php/doc-en commit 00b1185: the PDO attribute constants are typed int again, and PDO::getAttribute() documents in its changelog that PHP 8.4.0 returns bool for ATTR_AUTOCOMMIT, ATTR_EMULATE_PREPARES and MYSQL_ATTR_DIRECT_QUERY. The empty xi:fallback elements of pdo-dblib.xml are removed as well, as its EN-Revision now includes that upstream change. EN-Revision updated.

Fixed a few inaccurate sentences in reference/pdo/constants.xml along the way (missing default-mode sentence of ERRMODE_EXCEPTION, catalog/table name prefix wording, allocation/free events, a duplicated PDO:: in a method reference).

Fixes: #1374