src/bugsnag: fix polyfilling if requestAnimationFrame

Fixes #72 (`requestAnimationFrame` wrapper doesn't honor the passed
timestamp)

The old approach rely on `hijackTimeFunc`, which expects a callback to
accept at least two arguments. If the function being wrapped accepts
only argument, it is being swallowed.

Thanks-to: Jacob Marshall
Merge pull request #76 from bugsnag/72-fix-requestanimframe

src/bugsnag: fix polyfilling if requestAnimationFrame