Ruby » Ruby master

cont.c: fix compile error

• cont.c (rb_fiber_t): fix compile error caused by move to
  vm_core.h at r47964. [Feature #10341]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47969 b2dd03c8-39d4-4d8f-98ff-823fe69b080e