ViennaRNA 1.8.5 as a clean javascript class too

It is now possible to instantiate both libraries, but not simultaneously.

  var vrna = new LibVrna185;
  //...
  delete vrna;
  vrna = new LibVrna211;
  //...
  delete vrna;

will work fine, while

  var vrna1 = new LibVrna185;
  var vrna2 = new LibVrna211;

won't work as expected (both objects will use the v211 code)