internal.h: fix vm_state_version_t

* internal.h (vm_state_version_t): use uint64_t when it is larger than
  LONG_LONG, and fallback to unsigned long.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42826 b2dd03c8-39d4-4d8f-98ff-823fe69b080e