(bibtex-find-text, bibtex-remove-double-quotes-or-braces):

(bibtex-find-text, bibtex-remove-double-quotes-or-braces):
Support both kind of delimiters (braces or quotes) regardless of the
value of bibtex-field-left-delimiter and bibtex-field-right-delimiter.
(bibtex-field-left-delimiter, bibtex-field-right-delimiter):
Made buffer-local.

(bibtex-beginning-of-entry): At the beginning of an
entry, leave point at the beginning of that entry instead of
moving to the beginning of the previous one.
(bibtex-end-of-entry): Outside an entry, now move to the end of
the *previous* entry (i.e. bibtex-beginning-of-entry and
bibtex-end-of-entry are now idempotent).
(bibtex-sort-entries, bibtex-clean-entry): Removed now obsolete
calls of bibtex-beginning-of-entry just before calls to
bibtex-end-of-entry.
(bibtex-clean-entry): Minor change to adapt to new behavior of
bibtex-beginning-of-entry.