Returns the registry table. This is a special table used by C functions to store information it wants to keep isolated from Lua functions.
table.foreach (debug.getregistry (), print)
-->
FILE* table: 01B43F50
_LOADLIB table: 01B42BC0
mushclient.world table: 01B4BBC0
_LOADED table: 01B418C0
mushclient.document userdata: 017A8C58
pcre_regex_handle table: 01B4E830