hypot division by zero

["Dehmel, Rüdiger"]

Hello,

the hypot functions in libstdc++-v3/libmath/stubs.c
makes a "division by zero"  exception when hypot(0, 0) is called.

Some thing like:

if (s == 0) return (0.);

is missing.

Other hypot implementations have such a test.

Ruediger