[Swf9] print "undefined" as "null"

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Sync with Browser.hx 4681ab7fd8542.

git-svn-id: http://haxe.googlecode.com/svn/trunk@6096 f16182fa-f095-11de-8f43-4547254af6c6
[As3] we can only get public fields through Type reflection

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insupported is unsupported

git-svn-id: http://haxe.googlecode.com/svn/trunk@6098 f16182fa-f095-11de-8f43-4547254af6c6