Fix vertical whitespace around "Backups" section.
Reorganize "Buffers" section: Keep related content together.
Rename `zap-to-char` advice and reword docstring.
Rename `occur-rename-buffer-use-search-string` to
occur-rename-buffer-after-search-string` and add docstring. Turn it into
a function (used to be a command). Add function to `occur-hook` to make
Occur take care of buffer renaming automatically.
Make sure clipboard strings (added to the clipboard from outside of
Emacs) are not lost when killing content inside of Emacs before pasting
them.