Don't build new strings when parsing numbers from JSON.
Don't build new strings when parsing numbers from JSON.

Gave a measurable performance win in my not-so-scientific
benchmark, but JSON parsing is still so mind-numbingly slow
there has to be some pretty juicy low-hanging fruit.

playn/playn,playn/playn,thecocce/playn-1,tinkerstudent/playn,tinkerstudent/playn,ruslansennov/playn2,longtaoge/playn,playn/playn,longtaoge/playn,ruslansennov/playn2,rachelharvey/playn,rachelharvey/playn,thecocce/playn-1