recreate html files without splitting them (except for funcref)

This patch merges the many html files of one "chapter" into a single one.
Except for funcref, which is quite large.

The resulting sizes of the files is like that:

 286095  funcref-3.html
 179809  ca65.html
  77297  geos.html
  54860  cc65.html
  45711  ld65.html
  36901  atari.html
  31897  customizing.html
  26044  da65.html
  25729  funcref.html
  23531  funcref-2.html
  20509  intro.html
  19134  apple2enh.html
  ...

'funcref' and 'ca65' are still quite large, if you want I can regenerate them with splitting.