fix prototypes for PHP 8

[remicollet]

Test suite fails with 8.0.9

Running 5 tests
FAIL DB::DB_Error[db_error.phpt]
FAIL DB::Error 2[db_error2.phpt]
FAIL DB::factory[db_factory.phpt]
PASS DB::isManip[db_ismanip.phpt]
PASS DB::parseDSN[db_parsedsn.phpt]
wrote log to "/builddir/build/BUILD/php-pear-DB-1.11.0/DB-1.11.0/tests/run-tests.log"
TOTAL TIME: 00:00
2 PASSED TESTS
0 SKIPPED TESTS
3 FAILED TESTS:

With this patch

PASS DB::DB_Error[db_error.phpt]
PASS DB::Error 2[db_error2.phpt]
PASS DB::factory[db_factory.phpt]
PASS DB::isManip[db_ismanip.phpt]
PASS DB::parseDSN[db_parsedsn.phpt]
TOTAL TIME: 00:01
5 PASSED TESTS
0 SKIPPED TESTS