RTG-1339 Support post-quantum hybrid key exchange

Func spec: https://wiki.cfops.it/x/ZcBKHw

vendor/github.com/cloudflare/circl/math/fp448/fp_amd64.go

@@ -0,0 +1,43 @@
+//go:build amd64 && !purego
+// +build amd64,!purego
+
+package fp448
+
+import (
+	"golang.org/x/sys/cpu"
+)
+
+var hasBmi2Adx = cpu.X86.HasBMI2 && cpu.X86.HasADX
+
+var _ = hasBmi2Adx
+
+func cmov(x, y *Elt, n uint)  { cmovAmd64(x, y, n) }
+func cswap(x, y *Elt, n uint) { cswapAmd64(x, y, n) }
+func add(z, x, y *Elt)        { addAmd64(z, x, y) }
+func sub(z, x, y *Elt)        { subAmd64(z, x, y) }
+func addsub(x, y *Elt)        { addsubAmd64(x, y) }
+func mul(z, x, y *Elt)        { mulAmd64(z, x, y) }
+func sqr(z, x *Elt)           { sqrAmd64(z, x) }
+
+/* Functions defined in fp_amd64.s */
+
+//go:noescape
+func cmovAmd64(x, y *Elt, n uint)
+
+//go:noescape
+func cswapAmd64(x, y *Elt, n uint)
+
+//go:noescape
+func addAmd64(z, x, y *Elt)
+
+//go:noescape
+func subAmd64(z, x, y *Elt)
+
+//go:noescape
+func addsubAmd64(x, y *Elt)
+
+//go:noescape
+func mulAmd64(z, x, y *Elt)
+
+//go:noescape
+func sqrAmd64(z, x *Elt)