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
Merge branch 'v1.9.x' into sam_1425
Merge branch 'sam_1425' into v1.9.x
Merge branch 'v1.9.x' into next