pack.c: use LONG_LONG

* pack.c (NATINT_LEN_Q): do not use long long directly, use LONG_LONG
  instead.  fix compilation error on mswin.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40126 b2dd03c8-39d4-4d8f-98ff-823fe69b080e