Mapping: Restore point and restriction in current buffer.

Mapping: Restore point and restriction in current buffer.

Daniel Clemente writes:

    Hi. After you eval this (for instance to count the number of
    headlines under a tree):

     (org-map-entries 'ignore t 'tree)

    you end up with a different view of the buffer
    because (org-narrow-to-subtree) was called. This seems an
    unwanted side effect since narrowing is not org-map-entries' job.

     Should (save-excursion) be used inside (org-map-entries
    ... 'tree) ?

He is right, and save-restriction is needed as well.  This is
what this commit implements.