function lmap(new_keystroke, old_keystroke, domain, new_annotation) {
        if (_isDomainApplicable(domain)) {
            normal.addLurkMap(new_keystroke, old_keystroke);
        }
    }
Map a key sequence to another in lurk mode.

@param {string} new_keystroke a key sequence to replace
@param {string} old_keystroke a key sequence to be replaced
@param {regex} [domain=null] a Javascript regex pattern to identify the domains that this mapping works.
@param {string} [new_annotation=null] use it instead of the annotation from old_keystroke if provided.

@see map