declare typed_cast feature if we generate a typed cast while inlining

git-svn-id: http://haxe.googlecode.com/svn/trunk@5980 f16182fa-f095-11de-8f43-4547254af6c6
we actually only need the upcast detection for Cpp and As3

git-svn-id: http://haxe.googlecode.com/svn/trunk@5981 f16182fa-f095-11de-8f43-4547254af6c6