Illegal property name fix for legacy build

IE8 only officially supports es3, which doesn't allow keywords as property names. 6to5 converts quoted property names in object literals into non-quoted names, which breaks the legacy build in the `parseJSON` module. This works around it by building the object on the fly, since there doesn't seem to be a way to turn off this particular feature of 6to5... not that there really should be, as the warning is right there on the tin (to5). I would be more worried about it if it was a pervasive problem, but it looks like it's just the one place in a patch of code that only gets run on init. Is that reasonable?