Fix the hi+lo decomposition for 2/(3ln2).  The decomposition needs to be into 12+24 bits of precision for extra-precision multiplication, but was into 13+24 bits.  On i386 with -O1 the bug was hidden by accidental extra precision, but on amd64, in 2^32 trials the bug caused about 200000 errors of more than 1 ulp, with a maximum error of about 80 ulps.  Now the maximum error in 2^32 trials on amd64 is 0.8573 ulps.  It is still 0.8316 ulps on i386 with -O1.
Fix the hi+lo decomposition for 2/(3ln2).  The decomposition needs to
be into 12+24 bits of precision for extra-precision multiplication,
but was into 13+24 bits.  On i386 with -O1 the bug was hidden by
accidental extra precision, but on amd64, in 2^32 trials the bug
caused about 200000 errors of more than 1 ulp, with a maximum error
of about 80 ulps.  Now the maximum error in 2^32 trials on amd64
is 0.8573 ulps.  It is still 0.8316 ulps on i386 with -O1.

The nearby decomposition of 1/ln2 and the decomposition of 2/(3ln2) in
the double precision version seem to be sub-optimal but not broken.

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase