Made pool_t::worker_t fields be private.
Fixed indentation of things, especially public/private specifiers in extproc code.
Made js.hpp not include extproc headers (but added one to jsimpl.hpp).
Made jsimpl.hpp not include extproc headers.
Made rdb_protocol/pb_server.hpp not include extproc/pool.hpp.
Removed extproc dependency from rdb_protocol/protocol.hpp.
Moved extproc::spawner_t::info_t to extproc::spawner_info_t.
Removed extproc includes from import.hpp and serve.hpp.
Removed extproc include dependency from rdb_protocol/query_language.hpp.
Updated copyright notice in extproc/pool.hpp (and only had to recompile a few files).