merged TestStringTools into StringTools.unit

git-svn-id: http://haxe.googlecode.com/svn/trunk@6124 f16182fa-f095-11de-8f43-4547254af6c6
allow unop overloading on abstracts

git-svn-id: http://haxe.googlecode.com/svn/trunk@6125 f16182fa-f095-11de-8f43-4547254af6c6
recursively handle toString in DCE (fixed issue #1462)

git-svn-id: http://haxe.googlecode.com/svn/trunk@6126 f16182fa-f095-11de-8f43-4547254af6c6