Test fix for procedural ODBC pconn close

While this issue affects any driver, getting a driver into a state that
persists across persistent connections is driver specific, be it wedged
or just some connection variables. As such, just make an SQL Server
specific test, since that's the driver used in CI.

Author: NattyNarwhal

ext/odbc/tests/odbc_persistent_close.phpt

@@ -0,0 +1,65 @@
+--TEST--
+odbc_pconnect(): Make sure closing a persistent connection works
+--EXTENSIONS--
+odbc
+--SKIPIF--
+<?php
+
+include 'skipif.inc';
+
+// The test can affect multiple drivers, but testing it is driver-specific.
+// Since CI runs ODBC tests with SQL Server, just use an SQL Server specific way of testing.
+$conn = odbc_connect($dsn, $user, $pass);
+$result = @odbc_exec($conn, "SELECT @@Version");
+if ($result) {
+    $array = odbc_fetch_array($result);
+    $info = (string) reset($array);
+    if (!str_contains($info, "Microsoft SQL Server")) {
+       echo "skip MS SQL specific test";
+    }
+}
+?>
+--FILE--
+<?php
+
+include 'config.inc';
+
+// set a session specific variable via CONTEXT_INFO, if we get the same connection again, it should be identical
+function set_context_info($conn, $string) {
+	$hexstring = bin2hex($string);
+	return odbc_exec($conn, "SET CONTEXT_INFO 0x$hexstring"); /* '*' */
+}
+
+function fetch_context_info($conn) {
+	$stmt = odbc_exec($conn, "SELECT CONTEXT_INFO() AS CONTEXT_INFO");
+	if (!$stmt) {
+		return false;
+	}
+	$res = odbc_fetch_array($stmt);
+	if ($res) {
+		// this is a binary, so we get a bunch of nulls at the end
+		return $res["CONTEXT_INFO"] ? trim($res["CONTEXT_INFO"]) : null;
+	} else {
+		return false;
+	}
+}
+
+// run 1: set expectations
+$conn = odbc_pconnect($dsn, $user, $pass);
+set_context_info($conn, "PHP odbc_pconnect test");
+var_dump(fetch_context_info($conn));
+
+// run 2: reuse same connection (imagine this is another request)
+$conn = odbc_pconnect($dsn, $user, $pass);
+var_dump(fetch_context_info($conn));
+
+// run 3: close it and see if it's the same connection
+odbc_close($conn);
+$conn = odbc_pconnect($dsn, $user, $pass);
+var_dump(fetch_context_info($conn));
+
+?>
+--EXPECTF--
+string(22) "PHP odbc_pconnect test"
+string(22) "PHP odbc_pconnect test"
+NULL