(isearch-toggle-regexp): Set `isearch-success' and `isearch-adjusted' to `t'.

(isearch-toggle-regexp): Set `isearch-success' and `isearch-adjusted' to `t'.
(isearch-toggle-case-fold): Set `isearch-success' to `t'.
(isearch-message-prefix): Add "pending" for isearch-adjusted.
(isearch-other-meta-char): Restore isearch-point unconditionally.
(isearch-query-replace): Add new arg `regexp-flag' and use it.
Set point to start of match if region is not active in transient
mark mode (to include the current match to region boundaries).
Push the search string to `query-replace-from-history-variable'.
Add prompt "Query replace regexp" for isearch-regexp.
Add region beginning/end as last arguments of `perform-replace.'
(isearch-query-replace-regexp): Replace code by the call to
`isearch-query-replace' with arg `t'.