* win32/win32.c, include/win32/win32.h (rb_w32_set_nonblock): new
  function to support nonblock-mode of pipes.

* win32/win32.c (rb_w32_read): nonblock-mode pipe returns ERROR_NO_DATA
  if there is no data, but also returns it if remote-end is closed.

* win32/win32.c (rb_w32_write): if cannot to write any data, it may be
  blocking.

* io.c (rb_io_set_nonblock): use rb_w32_set_nonblock for Windows.

* ext/io/nonblock/nonblock.c (rb_io_nonblock_set): use ruby's API when
  setting nonblock-mode.

* test/ruby/test_io.rb: test nonblock pipes on Windows.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48361 b2dd03c8-39d4-4d8f-98ff-823fe69b080e