[cpp] Keep separate key map to ensure that references are held.  Fix toString
[cpp] Keep separate key map to ensure that references are held.  Fix toString

pleclech/hacking-haxe,pleclech/hacking-haxe,pleclech/hacking-haxe,pleclech/hacking-haxe,pleclech/hacking-haxe,pleclech/hacking-haxe