(bibtex-clean-entry): Disentangle code.
(bibtex-realign): New function.
(bibtex-reformat): Use mapcar and bibtex-realign. Do not use
bibtex-beginning-of-first-entry and bibtex-skip-to-valid-entry.
Remove undocumented optional arg called-by-convert-alien.
(bibtex-convert-alien): Use bibtex-realign. Use bibtex-reformat
for sorting instead of bibtex-sort-buffer.