* cygerrno.h: Make multi-inclusion safe.

* cygerrno.h: Make multi-inclusion safe.
* fhandler_termios.cc (fhandler_termios::tcsetpgrp): Deal with EINTR.
* dcrt0.cc (dll_crt0_0): Accommodate init_console_handler argument change.
* winsup.h: Ditto.
* fhandler_tty.cc (fhandler_tty_slave::open): Ditto.
* exceptions.cc (init_console_handler): Ditto.  Ignore console events if we're
not attached to a terminal.
* fhandler_tty.cc (fhandler_tty_slave::open): Ditto.
* wincap.cc: Implement has_null_console_handler_routine throughout.
* wincap.h: Ditto.