bpo-43833: Emit warnings for numeric literals followed by keyword (GH-25466)

Emit a deprecation warning if the numeric literal is immediately followed by
one of keywords: and, else, for, if, in, is, or. Raise a syntax error with
more informative message if it is immediately followed by other keyword or
identifier.

Automerge-Triggered-By: GH:pablogsal
(cherry picked from commit 2ea6d890281c415e0a2f00e63526e592da8ce3d9)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>