* lisp/isearch.el: Rename word search to regexp-function search

* lisp/isearch.el: Rename word search to regexp-function search

`isearch-word' went well beyond its original purpose, and the name
no longer makes sense.  It is now called
`isearch-regexp-function', and it's value should always be a
function that converts a string to a regexp (though setting it to
t is still supported for now).

(isearch-word): Make obsolete.
(isearch-regexp-function): New variable.
(isearch-mode, isearch-done, isearch--state, isearch--set-state)
(with-isearch-suspended, isearch-toggle-regexp)
(isearch-toggle-word, isearch-toggle-symbol)
(isearch-toggle-character-fold, isearch-query-replace)
(isearch-occur, isearch-highlight-regexp)
(isearch-search-and-update, isearch-message-prefix)
(isearch-search-fun-default, isearch-search)
(isearch-lazy-highlight-new-loop, isearch-lazy-highlight-search):
Use it.
(isearch-lazy-highlight-regexp-function): New var.
(isearch-lazy-highlight-word): Make obsolete.
(isearch--describe-regexp-mode): New function.
(isearch--describe-word-mode): Make obsolete.

* lisp/info.el (Info-isearch-search): Use the new var.

* lisp/replace.el (replace-search, replace-highlight): Use the new
var.

* lisp/obsolete/longlines.el (longlines-search-function): Use the
new var.

* lisp/hexl.el (hexl-isearch-search-function): Use the new var.

* lisp/cedet/semantic/senator.el (senator-isearch-search-fun): Use
the new var.