* fhandler.h (fhandler_pipe::create): Rename from the misnamed

* fhandler.h (fhandler_pipe::create): Rename from the misnamed
"create_selectable".  Change return to DWORD.
(fhandler_pty_common::pipesize): New constant.
* fhandler_fifo.cc (fhandler_fifo::fhandler_fifo): Reflect create_selectable
name change.
* miscfuncs.cc (CreatePipeOverlapped): Ditto.
* pipe.cc (fhandler_pipe::create): Ditto.
(fhandler_pipe::create): Rename from the misnamed "create_selectable".  Return
DWORD.  Only set pipe size to default when it is passed in as zero.
* fhandler_tty.cc (fhandler_pty_master::setup): Ditto.  Use
fhandler_pty_common::pipesize rather than a raw constant.
* tty.cc (tty::not_allocated): Ditto.
* sigproc.cc (sigproc_init): Use create_selectable to create the signal pipe to
get a more appropriate message based pipe.