bug#44171: Make cwarn.el obsolete

[Stefan Kangas]

cwarn.el is a package that highlights three types of "suspicious C and
C++ constructions".

;; * Assignments inside expressions, including variations like "+=".
;; * Semicolon following immediately after `if', `for', and `while'
;;   (except, of course, after a `do .. while' statement).
;; * C++ functions with reference parameters.

This was written in 1999, but is it useful today?

Modern compilers should warn about the above, and for the cases where
they don't, users are probably better off using a real linter (such as
cppcheck for C).

Should cwarn.el be obsoleted?