previous revision. Use log10f() instead of log10(). log10f() is
currently slightly slower than log10() on P5's, but it is potentially
significantly faster.
Fixed declaration of the C function used in the (unused?) KR_headers
case.
log10(x) = log10e * log(x). The formula would work if the RHS were
evaluated in extended precision with an extended precision log().
This actually happened with the i387 log() because it returns excess
precision.
Found by: ucbtest
