Add original unix v6

source/fort/rt1/csqrt.f

@@ -0,0 +1,14 @@
+	function csqrt(z1)
+	complex csqrt, z1, z2
+	dimension dummy(2)
+	equivalence (a,z2,dummy(1)), (b,dummy(2))
+
+	z2 = z1
+	c = cabs(z2)
+	c = sqrt(c)
+	b = atan2(b, a)/2.0
+	a = c*cos(b)
+	b = c*sin(b)
+	csqrt = z2
+	return
+	end