* vm.c: vm_clear_all_cache is not necessary now we use a 64 bit counter
  for global state version.

* vm_insnhelper.h: ruby_vm_global_state_version overflow is unnecessary

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43444 b2dd03c8-39d4-4d8f-98ff-823fe69b080e