merge revision(s) 39939: [Backport #8360]

	* thread.c (double2timeval): convert the infinity to TIME_MAX to avoid
	  SEGV by Thread.new {}.join(Float::INFINITY) on
	  Debian GNU/Linux (amd64).


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@40562 b2dd03c8-39d4-4d8f-98ff-823fe69b080e