Fixed commentary in +ff
A comment incorrectly indicated that `w` was a face for two different terms in the same arm.
::
:: w=width: bits in exponent field
:: p=precision: bits in fraction field
- :: w=bias: added to exponent when storing
+ :: b=bias: added to exponent when storing
:: r=rounding mode: same as in ++fl
::
++ sb (bex (^add w p)) :: sign bit
