* lisp/subr.el: Add discard-input to more functions.

* lisp/subr.el: Add discard-input to more functions.

* lisp/subr.el (read-char-from-minibuffer-insert-other)
(y-or-n-p-insert-other): Use discard-input in case of user mistake.
(do-after-load-evaluation): Add discard-input before calling 'message',
so in case of the active minibuffer, calling minibuffer-message will allow
sit-for to wait the complete timeout, because discard-input will discard
all initial events that prevent sit-for from waiting during startup.
https://lists.gnu.org/archive/html/emacs-devel/2019-11/msg00581.html