Fix AVM1 event broadcaster to correctly pass on arguments to listeners

Using `Array.prototype.slice.call(arguments, 1)` didn't work at all, but `...args` does.
Change AVM1 MovieClipLoader to pass target MovieClip to listeners instead of the MovieClipLoader itself
Merge pull request #1753 from tschneidereit/moviecliploader

AVM1 MovieClipLoader fixes