Global declaration needed for variables in kses.php

[Jaza613]

In 'wp-includes/kses.php', the three variables '$allowedposttags, $allowedtags, $allowedentitynames' are declared within an 'if' statement. Under normal circumstances, they end up in the global context as they should.

However, if the current PHP environment uses namespaces / autoload, they seem to not get added, resulting in this error:

Warning: in_array() expects parameter 2 to be array, null given in /path/to/wp-includes/kses.php line 1176

(Line 1176 is:)

return ( ( ! in_array($i, $allowedentitynames) ) ? "&$i;" : "&$i;" );

Attached patch fixes the issue, by declaring these variables with the 'global' keyword before assigning them a value.

[wonderboymusic]

In 28845:

In kses.php, ensure that $allowedposttags, $allowedtags, and $allowedentitynames are added to the global namespace.

Props Jaza613.
Fixes #28582.