Extract CSipHasher to it's own file in crypto/ directory.

This is a move-only commit with the exception of changes to includes.

src/bench/crypto_hash.cpp

@@ -14,6 +14,7 @@
 #include <crypto/sha1.h>
 #include <crypto/sha256.h>
 #include <crypto/sha512.h>
+#include <crypto/siphash.h>
 
 /* Number of bytes to hash per iteration */
 static const uint64_t BUFFER_SIZE = 1000*1000;