merge revision(s) r46495,r46499: [Backport #9971]

	signal.c: no cfunc frame at stack overflow

	* signal.c (check_stack_overflow): avoid pushing a cfunc frame,
  trying to fix stack overflow deadlock.
	* signal.c (check_stack_overflow): drop the last tag too close to
	  the fault page, to get rid of stack overflow deadlock.
	  [Bug #9971]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_1@47597 b2dd03c8-39d4-4d8f-98ff-823fe69b080e