Add isearch-yank-symbol-or-char

Add isearch-yank-symbol-or-char

* doc/emacs/search.texi (Isearch Yank): Document new
function, keybindings.

* etc/NEWS: Mention isearch changes.

* lisp/isearch.el (isearch--yank-char-or-syntax): New function.
(isearch-yank-word-or-char): Call it.
(isearch-yank-symbol-or-char): New function.
(isearch-mode-map): Change 'C-M-w' binding from
'isearch-del-char' to isearch-yank-symbol-or-char; add 'C-M-d'
binding for 'isearch-del-char'.