always optimize var initialization (fixed issue #1567)

git-svn-id: http://haxe.googlecode.com/svn/trunk@6369 f16182fa-f095-11de-8f43-4547254af6c6
give meaningful error when @:op functions cannot be accessed

git-svn-id: http://haxe.googlecode.com/svn/trunk@6370 f16182fa-f095-11de-8f43-4547254af6c6