Merge pull request #1248 from tschneidereit/nat

Cleanup and fixes in nat branch
Adds flash.net.URLStream unit tests
Added comment.
Add inverted concatenated matrix flag.
Some comments.
Merge branch 'nat' of https://github.com/mozilla/shumway into nat
Use isNullOrUndefined
flash.filters native implementation
Fix previous commit.
First attempt to fix but related to aliased event dispatcher lists.
Merge branch 'nat' of https://github.com/mozilla/shumway into nat
Fixes URLLoader check, adds simple NetConnection test
Add test case.
Merge branch 'nat' of https://github.com/mozilla/shumway into nat