Merge pull request #1460 from tschneidereit/nat

AVM1 stdlib improvements
Merge pull request #1461 from tschneidereit/nat

Fix formatting of BitmapData.ts to include space after colon in type declarations
Merge pull request #1462 from tschneidereit/nat

Support AS2 classes
Merge pull request #1463 from tschneidereit/nat

AVM1 fixes
Make the MovieClip constructor native

No need to generate code for this: we already have the correct native ctor in place.
Handle `gotoAnd*` calls on newly-created MovieClips, that don't yet have advanced to frame 1