call Array#lastIndexOf in .removeElement
call Array#lastIndexOf in .removeElement

leads to a speedup in `cornet` and doesn't hurt performance elsewhere

fasterize/domhandler,BuildingJarl/domhandler,fb55/domhandler,liuxiong332/node-domhandler2,simonfan/domhandler,mail-apps/domhandler,mail-apps/node-domhandler2