Sets an environment value as being checked for

@param key
@param value
function(key, value) {
      if (typeof key == "object") {
        var map = key;
        for (key in map) {
          this.__environmentChecks[key] = map[key];
        }
      } else if (value === undefined) {
        delete this.__environmentChecks[key];
      } else {
        this.__environmentChecks[key] = value;
      }
    }