(Search): Shorten introduction.

(Search): Shorten introduction.
(Basic Isearch): Add command table.  Discuss reverse isearch and
isearch highlighting.
(Repeat Isearch): Move lazy highlighting discussion here.  Add search
ring to cindex.
(Special Isearch): Move input methods discussion here.
(Non-ASCII Isearch): Node deleted, merged with Special Isearch.
(Isearch Yank): Node deleted, and contents moved into Basic Isearch and
Repeat Isearch.
(Isearch Minibuffer): New node.
(Word Search): Document new word search commands.
(Regexp Example): Simplify example using sentence-end-base variable.
(Replace): Reword introduction.
(Unconditional Replace): Remove unnecessary example.
(Other Repeating Search): Document new `M-s o' binding.