ruby/io.h: deprecate old macros

* include/ruby/io.h (rb_io_mode_flags, rb_io_modenum_flags):
  deprecate old macros for compatibility for ruby 1.8 and older.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47861 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2014-10-10

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47862 b2dd03c8-39d4-4d8f-98ff-823fe69b080e