Introduce autodefs to replace some settings

+ :popup -> set-popup-rule!
+ :popups -> set-popup-rules!
+ :company-backend -> set-company-backend!
+ :evil-state -> set-evil-initial-state!

I am slowly phasing out the setting system (def-setting! and set!),
starting with these.

What are autodefs? These are functions that are always defined, whether
or not their respective modules are enabled. However, when their modules
are disabled, they are replaced with macros that no-op and don't
waste time evaluating their arguments.

The old set! function will still work, for a while.

modules/completion/company/autoload.el

@@ -1,23 +1,30 @@
 ;;; completion/company/autoload.el -*- lexical-binding: t; -*-
 
+;;;###autodef
+(defun set-company-backend! (modes &rest backends)
+  "Prepends BACKENDS to `company-backends' in major MODES.
+
+MODES should be one major-mode symbol or a list of them."
+  (cl-loop for mode in modes
+           for def-name = (intern (format "doom--init-company-%s" mode))
+           do
+           (fset def-name
+                 (lambda () (when (or (eq major-mode mode)
+                                 (and (boundp mode) (symbol-value mode)))
+                         (require 'company)
+                         (make-variable-buffer-local 'company-backends)
+                         (dolist (backend backends)
+                           (cl-pushnew backend company-backends :test #'equal)))))
+           and do (add-hook (intern (format "%s-hook" mode)) def-name)))
+
+;; FIXME obsolete :company-backend
 ;;;###autoload
 (def-setting! :company-backend (modes &rest backends)
   "Prepends BACKENDS to `company-backends' in major MODES.
 
 MODES should be one major-mode symbol or a list of them."
-  `(progn
-     ,@(cl-loop for mode in (doom-enlist (doom-unquote modes))
-                for def-name = (intern (format "doom--init-company-%s" mode))
-                collect
-                `(defun ,def-name ()
-                   (when (and (or (eq major-mode ',mode)
-                                  (bound-and-true-p ,mode))
-                              ,(not (eq backends '(nil))))
-                     (require 'company)
-                     (make-variable-buffer-local 'company-backends)
-                     (dolist (backend (list ,@(reverse backends)))
-                       (cl-pushnew backend company-backends :test #'equal))))
-                collect `(add-hook! ,mode #',def-name))))
+  :obsolete set-company-backend!
+  `(set-company-backend! ,modes ,@backends))
 
 ;;;###autoload
 (defun +company/toggle-auto-completion ()