SLAPY2 - return sqrt(x**2+y**2), taking care not to cause
unnecessary overflow
REAL FUNCTION SLAPY2( X, Y )
REAL X, Y
SLAPY2 returns sqrt(x**2+y**2), taking care not to cause
unnecessary overflow.
X (input) REAL
Y (input) REAL X and Y specify the values x
and y.