mu4e: fix quotes in some docstrings

Escape correctly.

mu4e/mu4e-draft.el

@@ -100,7 +100,7 @@ symbols, for example:
 
   (setq mu4e-sent-messages-behavior (lambda ()
   (if (string= (message-sendmail-envelope-from) \"foo@example.com\")
-       \='delete \='sent)))
+       \\='delete \\='sent)))
 
 The various `message-' functions from `message-mode' are available
 for querying the message information."

mu4e/mu4e-main.el

@@ -361,7 +361,7 @@ Otherwise, do nothing."
 (defun mu4e--main-view ()
   "(Re)create the mu4e main-view, and switch to it.
 
-If `mu4e-split-view' equals \='single-window, show a mu4e menu
+If `mu4e-split-view' equals \\='single-window, show a mu4e menu
 instead."
   (if (eq mu4e-split-view 'single-window)
       (mu4e--main-menu)

mu4e/mu4e-org.el

@@ -52,7 +52,7 @@ Example usage:
                     \"No date\")))
       (concat subject \" \" date)))
 
-  (setq org-mu4e-link-desc-func \='my-link-descr)"
+  (setq org-mu4e-link-desc-func \\='my-link-descr)"
   :type '(function)
   :group 'mu4e-org)
 

mu4e/mu4e-search.el

@@ -89,7 +89,7 @@ Example that hides all trashed messages:
 
   (setq mu4e-search-hide-predicate
      (lambda (msg)
-       (member \='trashed (mu4e-message-field msg :flags)))).")
+       (member \\='trashed (mu4e-message-field msg :flags)))).")
 
 (defvar mu4e-search-hide-enabled t
   "Whether `mu4e-search-hide-predicate' should be active.