Log Message:
Update converters/bibtex2html to 1.88

Changes:
Version 1.88, 20/11/2007
========================
 o new option -revkeys to number entries in reverse order
   (patch by Walter Guttmann)
 o fixed bug with '\ ' (backslash space) introduced in version 1.82
   (shows up with -s gerplain)
 o \c{C}, \"y, \"Y  (patch by John Kewley)
 o \k (using unicode entities, patch by John Kewley)

Version 1.87, 16/07/2007
========================
 o \hat
 o \mathfrak (supported but no font change, as for \mathcal ad \mathbb)
 o \~a, \~A, \~o, and \~O
 o -- translated to – and --- to —

Version 1.86, 21/03/2007
========================
 o more accents macros: \oe \OE \~ \v \' \r