Refactored checked_convert_to_int to use number_as_integer.
Made datum serialization format use datum_serialized_type_t instead of datum_t::type_t.
Merge branch 'sam_1427' into sam_1426
Made datum serialization use varint serialization for numeric datums that are integral.
Merge branch 'next' into sam_1426
Removed unused number_as_integer declaration in datum.hpp.
Made blocker_pool_t be a class, not a struct.
Made the blocker pool specify the stack size for blocker pool threads to be the same as COROUTINE_STACK_SIZE (which is 128 KB).
Made us actually pass the stack size attr to pthread_create in the blocker pool.
re-adds protobuf_implementation to JS driver
Add missing "err." in the js driver

Review 879 by @neumino
JavaScript driver version 1.9.0-1
Made meta_op_t be meta_op_term_t.
Got rid of is_deterministic_impl.
Removed the backtrace_t::push_back helper function.
Removed unused dummy_frames argument from fourth exc_t constructor.
Removed unused dummy_frames parameter from runtime_check and the second exc_t constructor.
Turned runtime_check into runtime_fail.
Removed a bunch of unnecessary unreachable()s.
Used UNUSED in a place.