* tool/make-snapshot: pass the last revision in the last ChangeLog
  file without increment.

* tool/vcs.rb (export_changelog): exclude the beginning revision
  of the range uniformly. svn log includes it, but git log not.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@56656 b2dd03c8-39d4-4d8f-98ff-823fe69b080e