Inhibit quit in ElDoc timer functions (bug#45117)

Inhibit quit in ElDoc timer functions (bug#45117)

The point of un-inhibiting it was to make ElDoc backends interruptible
with any input (as in while-no-input), since that should in principle
invalidate the need of the current ElDoc processing.  But that
strategy is dangerous for backends that perform complex
synchronization with external processes.  Better let each backend
decide for itself it needs this eager interruptive behavior, like is
presumably the case with the Octave backend.

This reverts a part of

    commit 12e922156c86a26fa4bb2cb9e7d2b3fd639e4707
    Author: Stefan Monnier <monnier@iro.umontreal.ca>
    Date:   Tue Dec 4 18:15:44 2018 -0500

* lisp/emacs-lisp/eldoc.el (eldoc-print-current-symbol-info):

* lisp/progmodes/octave.el (octave-eldoc-function-signatures): Use
while-no-input.