doc-view-presentation, doc-view-fit-window-to-page, and use mutool

doc-view-presentation, doc-view-fit-window-to-page, and use mutool

* lisp/doc-view.el (doc-view-pdfdraw-program): Use "mutool" if available.
(doc-view-mode-map): Keep default 'g' binding of 'revert-buffer'.
Change 'r' binding to 'revert-buffer'.
(doc-view-revert-buffer): Make it an obsolete alias.
(doc-view--revert-buffer): Rename from doc-view-revert-buffer, change
calling convention for use in add-function.
(doc-view-fit-window-to-page): New command.
(doc-view-pdf->png-converter-mupdf): Make it work with "mutool".
(doc-view-mode): Use add-function for revert-buffer-function.
(doc-view-presentation-mode-map, doc-view-presentation--src-data):
New vars.
(doc-view-presentation-exit, doc-view-presentation-mode)
(doc-view-presentation--propagate-pn, doc-view-presentation):
New functions.