org.el (org-do-emphasis-faces): Fix false positives handling

org.el (org-do-emphasis-faces): Fix false positives handling

* org.el (org-do-emphasis-faces): Handle false positives by
restarting the re-search one char after the beginning of the
match, not one char before its ending.

Before this fix, consider this buffer

** Headline
  - *Bold* non-bold
  - *Bold* non-bold

The first false positive is "** Headline\n  - *Bold*"

Starting the search again from the last "*" will skip
the "*Bold*" string.  Starting again at "* Headline" will
find it.