* lisp/replace.el (perform-replace): Move let-bindings of isearch-*

* lisp/replace.el (perform-replace): Move let-bindings of isearch-*
variables deeper to the loop that searches for the next match.
Add bindings for `isearch-nonincremental' and `isearch-adjusted'.
Use `isearch-search-fun-default' instead of `isearch-search-fun'.

* lisp/isearch.el (isearch-search-fun-default): Check for null
first element of isearch-cmds as a precaution when it's used
with inactive isearch.