* errno.cc (errmap): Change mapping of NO_SYSTEM_RESOURCES to EFBIG.

* errno.cc (errmap): Change mapping of NO_SYSTEM_RESOURCES to EFBIG.
* fhandler.cc (MAX_OVERLAPPED_WRITE_LEN): New constant.
(MIN_OVERLAPPED_WRITE_LEN): Ditto.
(fhandler_base_overlapped::close): Accommodate change in arguments to
wait_overlapped.
(fhandler_base_overlapped::setup_overlapped): Add __stdcall and regparm
modifiers.
(fhandler_base_overlapped::destroy_overlapped): Ditto.
(fhandler_base_overlapped::has_ongoing_io): Ditto.
(fhandler_base_overlapped::wait_overlapped): Modify to return an enum returning
various states.  Accept nonblocking parameter.
(fhandler_base_overlapped::read_overlapped): Add __stdcall and regparm
modifiers.  Rework to attempt to be smarter about reacting to states returned
by wait_overlapped.
(fhandler_base_overlapped::write_overlapped): Ditto.  Add fallback option for
when wait_overlapped detects that smaller chunks must be written.
(fhandler_base_overlapped::write_overlapped_fallback): Ditto.
* fhandler.h (DEFAULT_PIPEBUFSIZE): Move definition here from pipe.cc.
(fhandler_base::has_ongoing_io): Define with __stdcall and regparm modifiers.
(fhandler_base_overlapped::wait_return): New enum.
(fhandler_base_overlapped::max_atomic_write): New variable.
(fhandler_base_overlapped:: wait_overlapped): Accommodate changes mentioned
above to arguments and modifiers.
(fhandler_base_overlapped::setup_overlapped): Ditto for modifiers.
(fhandler_base_overlapped::read_overlapped): Ditto.
(fhandler_base_overlapped::write_overlapped): Ditto.
(fhandler_base_overlapped::destroy_overlapped): Ditto.
(fhandler_base_overlapped::has_ongoing_io): Ditto.
(fhandler_base_overlapped::fhandler_base_overlapped): Zero max_atomic_write.
* fhandler_fifo.cc (fhandler_fifo::fhandler_fifo): Set max_atomic_write to the
size of the DEFAULT_PIPEBUFSIZE.
(fhandler_fifo::wait): Accommodate change in arguments to wait_overlapped.
* pipe.cc (fhandler_pipe::fhandler_pipe): Set max_atomic_write to the size of
the DEFAULT_PIPEBUFSIZE.
(fhandler_pipe::create_selectable): Allow minimum size of DEFAULT_PIPEBUFSIZE.
(DEFAULT_PIPEBUFSIZE): Delete here, move to fhandler.h.