Added /*jslint undersc: true */ to tell JSLint to allow underscores (not require camelCase)

This corresponds to my pull request for JSLint

https://github.com/douglascrockford/JSLint/pull/160

This will made ADsafe not generate any new errors from JSLint in case my JSLint pull request is accepted. (Can't say it will pass because it currently doesn't pass, but this will not introduce new errors).