architecture, mainly to avoid getting a SIGFPE signal sent
when calling strtod(3) with certain input.
The SIGFPE has been sent because the code was not aware that
a Gradual Underflow is handled in software via traps on the
Alpha architecture, but is not implemented in our Alpha kernel
layer.
With `Sudden_Underflow' defined, strtod(3) should not depend
on Gradual Underflow and adjust its calculations accordingly,
which means that other, more subtle errors than the sending of
SIGFPE could be solved by this.
Discussed with: bde
PR: alpha/12623
PR: alpha/17032
PR: alpha/43567
MFC after: 7 days
