When a callback throws an exception, we catch it, and then handle
the exception after the libcurl function that invoked the callback
returns.
But we weren't checking the exception after some libcurl calls that
could invoke callbacks, which leaked the exception object in RELEASE
builds, and asserted in DEBUG builds.
This change is mostly for FB internal organizational reasons.
Building is not effected beyond the fact that the target now
lands in hphp/hhvm/hhvm rather than src/hhvm/hhvm.
aalexandre