make-snapshot: fix stable snapshot

* tool/make-snapshot (package): VCS#branch_list expects glob a
  pattern string but not a regexp.  based on the patch by Vit
  Ondruch.  in [ruby-core:67064].  [Bug #10636]
* tool/vcs.rb (VCS::SVN#branch_list): strip newlines.
* tool/vcs.rb (VCS::GIT.get_revisions): retrieve modified time
  from toplevel log too.
* tool/vcs.rb (VCS::GIT#branch_list): yield for each lines.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48946 b2dd03c8-39d4-4d8f-98ff-823fe69b080e