RB_RESERVED_FD_P): added.  This C API is to limit to access
  fds which are used by RubyVM internal.  In this version of
  CRuby, return 1 if fd is communication pipe.
  If your application needs to close all file descriptors to
  preent resource leak, skip internal fds using this C API.
  We also define a macro RB_RESERVED_FD_P(fd).  So you can write
  #ifndef RB_RESERVED_FD_P
  #define RB_RESERVED_FD_P(fd) 0
  #endif
  for Ruby 1.9.2 or previous version to write compatible extensions.
  See [ruby-core:37727]
* thread_win32.c (rb_reserved_fd_p): added (return 0 for any fds).
* io.c (rb_io_initialize): raise ArgumentError if given fd is reserved by Ruby.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@32394 b2dd03c8-39d4-4d8f-98ff-823fe69b080e