ext/pdo_sqlite: add ATTR_SQL and ATTR_EXPANDED_SQL statement attributes

[iliaal]

Summary

Implements #21322 -- adds support for retrieving the SQL text of a prepared PDO SQLite statement via PDOStatement::getAttribute(), mirroring SQLite3Stmt::getSQL().

Two new statement attributes on Pdo\Sqlite:

• ATTR_SQL -- returns the original SQL text (sqlite3_sql())
• ATTR_EXPANDED_SQL -- returns SQL with bound parameters expanded (sqlite3_expanded_sql(), guarded by configure check)

$stmt = $db->prepare('SELECT :name AS greeting');
$stmt->bindValue(':name', 'hello');
$stmt->execute();

$stmt->getAttribute(Pdo\Sqlite::ATTR_SQL);          // "SELECT :name AS greeting"
$stmt->getAttribute(Pdo\Sqlite::ATTR_EXPANDED_SQL); // "SELECT 'hello' AS greeting"

Changes

• php_pdo_sqlite_int.h -- new enum values PDO_SQLITE_ATTR_SQL, PDO_SQLITE_ATTR_EXPANDED_SQL
• sqlite_statement.c -- handle new attributes in pdo_sqlite_stmt_get_attribute()
• config.m4 / config.w32 -- configure check for sqlite3_expanded_sql
• pdo_sqlite.stub.php + pdo_sqlite_arginfo.h -- PHP-visible constants
• New test pdo_sqlite_getattr_sql.phpt, updated pdo_sqlite_constants.phpt

Feature addition is fairly small, I don't think it needs an RFC.

Implements feature request #21322