Fix interpretation of errorsAvm1 setting in generateActionCalls

Currently, the error handling wrapper is installed if the flag is set to `false`, where it should be the other way around.
Implement AVM1 globals `escape` and `unescape`
Use different index variable for inner loop in FrameDelta#_applyCommands
Fix AS2MovieClip's _insertChildAtDepth to make createEmptyMovieClip work
Don't try to send a complete message if an XHR request failed
Replace all uses of try/finally, because JS engines really do not like that
Merge pull request #1406 from tschneidereit/nat

Various fixes, mostly AVM1-related