Previous cleanup resurrected multiple class names, so
we know now the original alignment of a float.
Use them in 'web' mode, as it allows floats to be nearer
the section they are refering to, and it may limit
floats truncation in page splitting.
But keep floats aligned on a single side in 'book' mode,
as it might allow easier reading.
poire-z
8ffb9aff64