allow user report of some errors with HAXEDEBUG=1 env var (keep different from OCAMLRUNPARAM)

git-svn-id: http://haxe.googlecode.com/svn/trunk@6367 f16182fa-f095-11de-8f43-4547254af6c6
tells which file has issue when failing some 24 bit PNG decoding

git-svn-id: http://haxe.googlecode.com/svn/trunk@6368 f16182fa-f095-11de-8f43-4547254af6c6
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
abstract cleanup (fixed issue #1593)

git-svn-id: http://haxe.googlecode.com/svn/trunk@6371 f16182fa-f095-11de-8f43-4547254af6c6