* lisp/help-fns.el (help-fns-describe-variable-functions): New hook

* lisp/help-fns.el (help-fns-describe-variable-functions): New hook

(help-fns--compiler-macro, help-fns--parent-mode, help-fns--obsolete)
(help-fns--interactive-only): Indent output by 2 spaces.
(help-fns--side-effects): New function extracted from
describe-function-1.
(help-fns-describe-function-functions): Use it.
(help-fns--first-release, help-fns--mention-first-release): New functions.
(help-fns-function-description-header): Keymaps and macros can't
be interactive.
(help-fns--ensure-empty-line): New function.
(describe-function-1): Use it.
(help-fns--var-safe-local, help-fns--var-risky)
(help-fns--var-ignored-local, help-fns--var-file-local)
(help-fns--var-watchpoints, help-fns--var-obsolete)
(help-fns--var-alias, help-fns--var-bufferlocal): New functions,
extacted from describe-variable.
(describe-variable): Run help-fns-describe-variable-functions instead.