Avoid conflicts for backup, view, and undo dirs

vim/.config/vim/init.d/xdg.vim

@@ -11,10 +11,10 @@ set runtimepath+=$XDG_DATA_HOME/vim
 set packpath^=$XDG_DATA_HOME/vim
 call mkdir($XDG_DATA_HOME.'/vim/spell', 'p', 0700)
 
-set backupdir=$XDG_CACHE_HOME/vim/backup | call mkdir(&backupdir, 'p', 0700)
+set backupdir=$XDG_CACHE_HOME/vim/backup//  | call mkdir(&backupdir, 'p', 0700)
 set directory=$XDG_CACHE_HOME/vim/swap//    | call mkdir(&directory, 'p', 0700)
-set undodir=$XDG_CACHE_HOME/vim/undo     | call mkdir(&undodir,   'p', 0700)
-set viewdir=$XDG_CACHE_HOME/vim/view     | call mkdir(&viewdir,   'p', 0700)
+set undodir=$XDG_CACHE_HOME/vim/undo//      | call mkdir(&undodir,   'p', 0700)
+set viewdir=$XDG_CACHE_HOME/vim/view//      | call mkdir(&viewdir,   'p', 0700)
 
 if !has('nvim')
   set viminfofile=$XDG_CACHE_HOME/vim/viminfo