bug#15383: universal-argument-num-events is void

[Juri Linkov]

Typing `C-s C-u C-l' reports the error:

  Symbol's value as variable is void: universal-argument-num-events

I wonder how it's possible to fix `isearch-other-meta-char'
to not use the removed `universal-argument-num-events'?

Just removing `universal-argument-num-events' causes other errors.

Interestingly, removing it from `isearch-mode-keep-pred'
(a replacement of `isearch-other-meta-char' that
I'm writing in bug#15200) causes no errors, but currently
`isearch-mode-keep-pred' has other problems, e.g.
`C-s C-l' exits Isearch, but `C-s C-u C-l' doesn't
(it should).  I'm looking for a fix.