* Fix class inheritance in IE9 & IE10 (T3041)
Internet Explorer 9&10 do not support __proto__ at all, don't have
Object.setPrototypeOf(), but have Object.getPrototypeOf().
Because of this setting the prototype is not possible, which makes the
babelHelpers.inherits() function to set __proto__ although not supported.
Afterwards Object.getPrototypeOf() is used, but this one is not
respecting the "custom" property __proto__ that we set.
The solution is to check for __proto__ first and afterwards fallback to
Object.getPrototypeOf().
* Do the same logic in babel-helper-replace-supers
* Fix tests
* Extract creation of prototype nodes to small helper
As an artificat of compiling methods to named function expressions the
function name is being considered a "local" binding in the function
body. This means that we will throw errors anytime someone would want to
create a new local binding with the same name.
This is solved by assigning a symbol to function Identifiers that
indicates that they should not be considered local bindings.
