win32ole.rb: use TracePoint

* ext/win32ole/lib/win32ole.rb: use TracePoint to hook all thread
  creation not only by Thread.new and to get rid of interference with
  svar scope.  [Bug #7681] [ruby-core:51365]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@38848 b2dd03c8-39d4-4d8f-98ff-823fe69b080e