Ruby

• vm.c (backtrace_*): change type of lev and n from size_t to int.
  Also set type of rb_backtrace_t#backtrace_size to int.
  A patch from nobu.
• vm_eval.c: ditto.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@35807 b2dd03c8-39d4-4d8f-98ff-823fe69b080e