Use X64 ASM ed25519 signatures on Linux/x64, which are about 10X faster. Will matter a lot for network controllers, not so much for other things.

ext/ed25519-amd64-asm/fe25519_getparity.c

@@ -0,0 +1,8 @@
+#include "fe25519.h"
+
+unsigned char fe25519_getparity(const fe25519 *x)
+{
+  fe25519 t = *x;
+  fe25519_freeze(&t);
+  return (unsigned char)t.v[0] & 1;
+}