keep Null/SNull when building SData/SEnum fields (fixed issue #1709)

git-svn-id: http://haxe.googlecode.com/svn/trunk@6537 f16182fa-f095-11de-8f43-4547254af6c6
removed AccCall _ warnings (ocaml 4.0+ only?)

git-svn-id: http://haxe.googlecode.com/svn/trunk@6538 f16182fa-f095-11de-8f43-4547254af6c6
fixed corrupted swf (fixed issue #1439)

git-svn-id: http://haxe.googlecode.com/svn/trunk@6539 f16182fa-f095-11de-8f43-4547254af6c6