merge revision(s) 41266: [Backport #8517]

	* ext/socket/extconf.rb:  Enable RFC 3542 IPV6 socket options for OS X
	  10.7+.  [ruby-trunk - Bug #8517]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@41320 b2dd03c8-39d4-4d8f-98ff-823fe69b080e