Version 1.49.91

- Deprecation: The private "__name__" property on Lang.Class instances is
  now discouraged. Code should not have been using this anyway, but if it did
  then it should use the "name" property on the class (this.__name__ should
  become this.constructor.name), which is compatible with ES6 classes.

- Closed bugs:

  * Use ES6 classes [#785652, Philip Chimento]
  * A few fixes for stack traces and error reporting [#786183, Philip Chimento]
  * /proc/self/stat is read for every frame if GC was not needed [#786017,
    Benjamin Berg]

- Build fix [Philip Chimento]