Skip fb4_datatypes*.phpt for Firebird server < 4.0.0 (GH-15354)

Using a newer fbclient version with an older server is generally
supported, and as such we must not only skip these tests for older
fbclients, but also for older servers.

In lack of some readily available function, we're querying the server
to find its version.

Author: cmb69

ext/pdo_firebird/tests/fb4_datatypes.phpt

@@ -7,6 +7,13 @@ pdo_firebird
 if (Pdo\Firebird::getApiVersion() < 40) {
 	die('skip: Firebird API version must be greater than or equal to 40');
 }
+require 'testdb.inc';
+$dbh = getDbConnection();
+$stmt = $dbh->query("SELECT RDB\$get_context('SYSTEM', 'ENGINE_VERSION') AS VERSION FROM RDB\$DATABASE");
+$data = $stmt->fetch(\PDO::FETCH_ASSOC);
+if (!$data || !array_key_exists('VERSION', $data) || version_compare($data['VERSION'], '4.0.0') < 0) {
+	die("skip Firebird Server version must be greater than or equal to 4.0.0");
+}
 ?>
 --XLEAK--
 A bug in firebird causes a memory leak when calling `isc_attach_database()`.

ext/pdo_firebird/tests/fb4_datatypes_params.phpt

@@ -7,6 +7,13 @@ pdo_firebird
 if (Pdo\Firebird::getApiVersion() < 40) {
 	die('skip: Firebird API version must be greater than or equal to 40');
 }
+require 'testdb.inc';
+$dbh = getDbConnection();
+$stmt = $dbh->query("SELECT RDB\$get_context('SYSTEM', 'ENGINE_VERSION') AS VERSION FROM RDB\$DATABASE");
+$data = $stmt->fetch(\PDO::FETCH_ASSOC);
+if (!$data || !array_key_exists('VERSION', $data) || version_compare($data['VERSION'], '4.0.0') < 0) {
+	die("skip Firebird Server version must be greater than or equal to 4.0.0");
+}
 ?>
 --XLEAK--
 A bug in firebird causes a memory leak when calling `isc_attach_database()`.