DLAPY3 - return sqrt(x**2+y**2+z**2), taking care not to
cause unnecessary overflow
DOUBLE PRECISION FUNCTION DLAPY3( X, Y, Z )
DOUBLE PRECISION X, Y, Z
DLAPY3 returns sqrt(x**2+y**2+z**2), taking care not to
cause unnecessary overflow.
X (input) DOUBLE PRECISION
Y (input) DOUBLE PRECISION Z (input)
DOUBLE PRECISION X, Y and Z specify the values x,
y and z.