merge revision(s) 39742,39743: [Backport #8005]

	assertions.rb: private flag

	* lib/test/unit/assertions.rb (assert_respond_to): accept optional
  include-private flag.
	* vm_method.c (rb_export_method): directly override the flag of method
	  defined in prepending class too, not adding zsuper entry.
	  [ruby-core:53106] [Bug #8005]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@40252 b2dd03c8-39d4-4d8f-98ff-823fe69b080e