With MySQL use cast(okey as unsigned) instead of cast(okey as integer)

The autologin ("Save information") functionality in 2.3.1 is broken since

    commit 52a41b3
    CommitDate: Fri Mar 23 18:01:32 2018 +0100

	Rework autologin to use a token approach

Although a cookie serendipity[author_autologintoken] with correct
expiration (one month) which random data content is present as value
in the serendipity_options table with name autologin_Username and
correct timestamp as okey and that is found with manually executing
the SQL statement

  SELECT name, value, okey FROM serendipity_options WHERE name = 'autologin_Username' AND okey > 1565801743 LIMIT 1

like done in include/functions_config.inc.php
serendipity_checkAutologin(), the login is forgotten after 30 minutes
or so. That was not the case with 2.1.5 where the login was valid for
weeks.

Of

    if (stristr($serendipity['dbType'], 'sqlite')) {
        $cast = "okey";
    } else {
        // Adds explicits casting for mysql, postgresql and others.
        $cast = "cast(okey as integer)";
    }

from which $cast then is used in the SQL statement instead of a plain
okey; when doing that manually with

  SELECT name, value, okey FROM serendipity_options WHERE name = 'autologin_Username' AND cast(okey as integer) > 1565801743 LIMIT 1

it produces the MySQL error

  #1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'integer) > 1565801743 LIMIT 1' at line 1

This also with $serendipity['dbType'] = 'mysqli' for the above code.

Indeed, cast(okey as integer) is invalid in MySQL and should be
cast(okey as unsigned) instead which then also works manually, see
https://stackoverflow.com/a/12127022 and
https://dev.mysql.com/doc/refman/5.7/en/cast-functions.html#function_cast

Same in serendipity_issueAutologin().

Changing those two places accordingly resolves the autologin not
persistent problem.

Additionally, inspecting the serendipity_options table revealed loads
of old serendipity[author_authorinformation] cookie information that
was never deleted in serendipity_issueAutologin() with the

  OR (okey LIKE 'l_%' AND $cast < " . (time() - 1814400) . ")")

expression producing a MySQL error. This has to be done manually
once as also 2.3.1 will not delete it anymore.

include/functions_config.inc.php

@@ -435,8 +435,11 @@ function serendipity_issueAutologin($user) {
     // Delete possible current cookie. Also delete any autologin keys that smell like 3-week-old, dead fish.
     if (stristr($serendipity['dbType'], 'sqlite')) {
         $cast = "okey";
+    } elseif (stristr($serendipity['dbType'], 'mysqli')) {
+        // Adds explicit casting for mysql.
+        $cast = "cast(okey as unsigned)";
     } else {
-        // Adds explicits casting for mysql, postgresql and others.
+        // Adds explicit casting for postgresql and others.
         $cast = "cast(okey as integer)";
     }
 
@@ -460,8 +463,11 @@ function serendipity_checkAutologin($user) {
 
     if (stristr($serendipity['dbType'], 'sqlite')) {
         $cast = "okey";
+    } elseif (stristr($serendipity['dbType'], 'mysqli')) {
+        // Adds explicit casting for mysql.
+        $cast = "cast(okey as unsigned)";
     } else {
-        // Adds explicits casting for mysql, postgresql and others.
+        // Adds explicit casting for postgresql and others.
         $cast = "cast(okey as integer)";
     }