Fix typos in docstrings.

Fix typos in docstrings.

* cus-edit.el (customize-apropos-options, custom-comment)
  (custom-comment-tag, custom-face-edit-attribute-tag):
  Fix typos in docstrings.
  (custom-buffer-done-kill): Remove * from defcustom docstring.
  (custom-file): Fix typo in doc of defcustom choice.

* frame.el (display-visual-class): Fix typo in docstring.
  (initial-frame-alist, minibuffer-frame-alist, pop-up-frame-alist)
  (special-display-frame-alist, show-trailing-whitespace)
  (auto-hscroll-mode, blink-cursor-delay, blink-cursor-interval)
  (display-hourglass, hourglass-delay, cursor-in-non-selected-windows):
  Remove * from defcustom docstrings.

* md4.el (md4-buffer): Fix typo in docstring.
  (md4, md4-64): Doc fixes.
  (md4-pack-int32): Reflow docstring.

* paths.el (rmail-file-name): Remove * from defcustom docstring.
  (prune-directory-list, gnus-nntp-service): Fix typos in docstrings.

* rect.el (open-rectangle): Reflow docstring.
  (spaces-string): Fix docstring typo.  Use "?\s" instead of "? ".

* select.el (x-get-cut-buffer): Fix typo in docstring.

* timezone.el (timezone-zone-to-minute, timezone-time-from-absolute)
  (timezone-time-zone-from-absolute, timezone-leap-year-p):
  Fix typos in docstrings.

* emacs-lisp/assoc.el (asort, aelement, aput, aget, amake):
  Fix typos in docstrings.