The cephes test vectors for tanh(3) in our libm fail on most

The cephes test vectors for tanh(3) in our libm fail on most
architectures.  On i386 they pass as the 80387 FPU uses 10 byte
numbers internaly.  But with standard 8 byte IEEE numbers, the monot
double precision test fails.
Relax the precision requirement for tanh(3), it is good enough.
OK martynas@