Allow multiple keymaps in :map argument

[fishyfriend]

This PR augments bind-keys to support passing a list of keymaps as the :map argument.

When one wants to bind the same key/command pair in multiple keymaps, the current options have some drawbacks:

;; Option 1: Code duplication, problematic when duplicated keybindings are numerous
(use-package foopkg
   :bind (:map bar-mode-map
          ("C-c x" . foocmd1)
          ("C-c y" . foocmd2)
          :map baz-mode-map
          ("C-c x" . foocmd1)
          ("C-c y" . foocmd2)))

;; Option 2: Use a loop, sacrificing the convenience and readability of :bind
(use-package foopkg
  :commands (foocmd1 foocmd2)
  :init
  (dolist (map (list bar-mode-map baz-mode-map))
    (bind-keys :map map
               ("C-c x" . foocmd1)
               ("C-c y" . foocmd2))))

With the new way, it is possible to avoid duplication and still use :bind:

(use-package foopkg
  :bind (:map (bar-mode-map baz-mode-map)
        ("C-c x" . foocmd1)
        ("C-c y" . foocmd2)))

Additionally this PR clarifies the documentation of bind-chords to reflect that this style is already available for that command.

[jwiegley]

Conflicts need resolving, please.

[fishyfriend]

The expansion in this test is not equivalent to the prior test as might be expected. The repeat-map property is applied to bound commands even after an intervening :map directive. This seems fishy to me but is existing behavior (the tests both pass independently of the changes in this PR). I'll leave this alone for now, but happy to open an issue if the behavior is indeed incorrect.

[fishyfriend]

I've removed this condition (not (memq map '(global-map override-global-map))) and the same condition again below. I do not understand their purpose, but informal testing leads me to believe these are safe to remove. E.g., if I specify :map override-global-map with :prefix-map or :repeat-map, the behavior is the same as if these checks were not in place.

[fishyfriend]

Hi @jwiegley, thanks. I've revised this and resolved the conflicts. I made one assumption that could use a second-guess, please see this comment. Other than that, it should be good to go. Cheers, Jacob. (cc: @Hugo-Heagren)

[jwiegley]

I was unable to update this PR directly, so I've opened another PR with the same changes @fishyfriend.