bug#15568: Lookup this-command-keys without a prefix argument

[Stefan Monnier <monnier@iro.umontreal.ca>]

> Also I discovered that to support a key sequence like
> `C-s C-u C-u C-l' requires adding the command `universal-argument-more'
> (and `universal-argument-minus' for completeness).

Indeed, tho I think your fix is a workaround rather than a real fix:
Basically after the first C-u we're in some kind of transient
"universal-argument mode" and isearch shouldn't have to know the list of
commands that can be run in this mode, it should instead just "wait for
the mode to exit".

This is a general issue regarding interaction between various uses of
set-temporary-overlay-map (and friends, since isearch doesn't actually
use set-temporary-overlay-map).  There should be some kind of notion of
nesting, where the outer set-temporary-overlay-map should not exit as
long as the inner one is still active.

> I installed a fix for these problems.

Thanks.


        Stefan