updated proto file
Removed locally used helper function declaration from depth_first_traversal.hpp.
Made handle_pair take a dft_value_t, added movable_t and counted_buf_lock_t.
Added a btree_concurrent_traversal stub implementation, that lacks real concurrency.
Holy crap, it works.  Made us load data concurrently off of disk when doing an rget.  Have not run any benchmarks so far.
Made concurrent btree traversal use an adjustable semaphore.
Actually initialized sink_waiters_.
Renamed dft_value_t to scoped_key_value_t.
Added a useful comment about scoped_key_value_t.
Fixed return value behavior of btree_concurrent_traversal.
Moved last_considered_key update into the exclusive zone.
Made comments more grammary.
Moved func_cache_t out of env_t.
Moved global_optargs_t out of env_t.
Separated gensym_t out from env_t.
Moved scopes_t out of env_t.
Moved implicit_vars_t out of env_t.
Moved cluster_env_t out of env_t.
Gave throw_if_interruptor_pulsed a friendly  THROWS_ONLY declaration.
Made env_t::this_machine be const.