keybinding: add keysymWeirdsMap

allow 'control-`' as shortcut

tower:
https://tower.im/projects/8f19f0bf0e754f0b82ef2c24bc230973/todos/da8e12b40e394c2a884597d0bf575071/

Change-Id: Ifb3ecf3620d0b36bb81211bcc0d35da7f02b0872