Removed unused boost headers from func.hpp.
Renamed good_func_t to reql_func_t.
Removed largely redundant reql_func_t constructor.
Removed redundant js_func_t constructor.
Renamed on_good_func method to on_reql_func (to match existing reql_func_t renamage).
Replaced counted_t<const func_t> with counted_t<func_t> everywhere (since func_t is an immutable type anyway).