Add missing external tags (Issue #119)

Author: k-takata

tools/untranslated.vim

@@ -5,4 +5,7 @@ let g:makehtml_external_taglinks = {
   \ 'version6.txt': 'http://vim-jp.org/vimdoc-ja/version6.html',
   \ 'version7.txt': 'http://vim-jp.org/vimdoc-ja/version7.html',
   \ 'version8.txt': 'http://vim-jp.org/vimdoc-ja/version8.html',
+  \ 'i_CTRL-B-gone': 'http://vim-jp.org/vimdoc-en/version5.html#i_CTRL-B-gone',
+  \ 'new-diff-mode': 'http://vim-jp.org/vimdoc-en/version6.html#new-diff-mode',
+  \ 'todo': 'http://vim-jp.org/vimdoc-en/todo.html#todo',
   \ }