Add original unix v6

source/fort/rt1/dcsqrt.f

@@ -0,0 +1,14 @@
+	function dcsqrt(z1)
+	double complex dcsqrt, z1, z2
+	double precision dummy(2), a, b, c
+	equivalence (a,z2,dummy(1)), (b,dummy(2))
+
+	z2 = z1
+	c = dcabs(z2)
+	c = dsqrt(c)
+	b = datan2(b, a)/2.0d0
+	a = c*dcos(b)
+	b = c*dsin(b)
+	dcsqrt = z2
+	return
+	end