#41 Update FAQ for ff page range markup

[Joachim Schrod]

Currently the FAQ gives xindy clauses that don't work
out of the box.

Point out -M ff-ranges and -M ff-ranges-only.
Maybe add an explanation how to get different markup:
i.e., the current one, but with the correct location
class "arabic-page-numbers" and with its redefinition
to have a min-range-length of 1. Add also a hint to the
warning about the redefinition and that this is ticket
1008050.