master f6967d2 1/3: Allow for the completion buffer to be automatically selected

[Daniel Martín]

I don't think I like this change to the minibuffer defaults.  It breaks
muscle memory and IMO is more incovenient when you need to show the
completion list many times.

One typical workflow I have is doing something like C-x C-f TAB TAB to
see the list of completions and then continue typing to narrow the list
of completions.  After this commit, you need to switch back to the
minibuffer to continue completing things, which is annoying.

I'd prefer that the new setting completion-auto-select is not enabled by
default.  What do other people think?