Changed search response and regexp search.

* src/epdfinfo.c (cmd_search_regexp): Merge rectangles directly.
  Changed response order.
  (cmd_search_string): Changed response order.
* lisp/pdf-info.el (pdf-info-query--transform-response): Handle new response order.

  (pdf-info-search-string): Changed the signature to make it
  comparable to other functions, i.e file-or-buffer should be the
  final argument.

  (pdf-info-search-regexp): Dito.

* lisp/pdf-occur.el (pdf-occur): Apply new signature.

* lisp/pdf-isearch.el
  (pdf-isearch-search-page,pdf-isearch-find-next-matching-page): Apply new signature.
Merge branch 'isearch-regexp'
Fixed a test.