merge revision(s) r46151,r46165: [Backport #9865]

	* io.c (rb_io_fileno, rb_io_inspect): non-modification does not
	  error on frozen IO.  [ruby-dev:48241] [Bug #9865]

	* io.c (rb_io_autoclose_p): Don't raise on frozen IO.

	* test/lib/minitest/unit.rb: IO#autoclose? may raise IOError.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_1@47140 b2dd03c8-39d4-4d8f-98ff-823fe69b080e