v1.12 of thinks.el

Drop the code that attempts to support XEmacs. I've got no way of sensibly using XEmacs at the moment so I have no way of even knowing if the code works any more. As such it makes sense to not even pretend to support it.

v1.11 of thinks.el

Minor tweaks that accept that we're no longer in the 1990s (loop to cl-loop swap and removal of * from the start of defcustom doc-strings).

v1.10 of thinks.el

Mostly just a code-tidy. Includes things like better package headers and dragging the code into a more modern era of emacs (in other words, cl is now cl-lib and defcustom has been part of Emacs for a while).