Support for OEM-8 key (right CTRL) in keymaps

Currently there is support for Shift and AltGr for modifiers, but some keyboard configurations has options for a third modifier, like CMS (Canadian Multilingual Standard). The modifier is the right CTRL key, or OEM-8 as mentionned in this website: https://kbdlayout.info/kbdcan/overview+virtualkeys

There is currently 2 bits available (10 and 11) for the keymap.