(bibtex-font-lock-url-regexp):

(bibtex-font-lock-url-regexp):
Use delete-dups when calculating the initial value.
(bibtex-autokey-get-title): Use <=.
(bibtex-goto-line): New function.
(bibtex-reposition-window): Use line numbers instead of point positions.
Use window-body-height.
(bibtex-find-crossref): Use bibtex-reposition-window.
(bibtex-find-entry): Use bibtex-reposition-window.  Always return
position of entry if key is found or nil if not found.