* gc.c (mark_current_machine_context): Call SET_STACK_END.
  This reverts a hunk of r40703 by ko1.
  This fixes [ruby-dev:48098] [Bug #9717].


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git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45543 b2dd03c8-39d4-4d8f-98ff-823fe69b080e