* st.c (st_add_direct): int is not always same with st_index_t.  some
  version of clang reports error.

* thread.c (vm_living_thread_num): ditto.
  reported by d6rkaiz (Isao Sugimoto) at [ruby-dev:47096]
  [Backport #7946]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_9_3@39503 b2dd03c8-39d4-4d8f-98ff-823fe69b080e