bug#55905: warn about misplaced or duplicated doc strings, `declare` or `interactive` forms

[Mattias Engdegård]

In function definitions, doc strings, `declare` and `interactive` forms are 
each optional but must appear in that order and duplications are not permitted. 
Many violations against these rules go undetected.

The attached patch adds checks to `defun` and `defmacro`. Violations result in 
compilation warnings but it could be changed into hard errors if desired. It 
also accepts `(:documentation EXPR)` as alternative to a doc string literal, 
which currently doesn't work i all cases.

Applying it reveals a handful of mistakes in the Emacs source tree, and in some 
external packages.

0001-function-and-macro-attribute-order-warning-patch.patch
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