[As3] moved $ prefix detection to genas3

git-svn-id: http://haxe.googlecode.com/svn/trunk@6639 f16182fa-f095-11de-8f43-4547254af6c6
null closure now returns null (fixed issue #1788)

git-svn-id: http://haxe.googlecode.com/svn/trunk@6640 f16182fa-f095-11de-8f43-4547254af6c6
[As3] fix for the accessor fix

git-svn-id: http://haxe.googlecode.com/svn/trunk@6641 f16182fa-f095-11de-8f43-4547254af6c6
use manual property to allow As3 compilation

git-svn-id: http://haxe.googlecode.com/svn/trunk@6642 f16182fa-f095-11de-8f43-4547254af6c6