Add UtxoSetHash file to manage UTXO set hashes

The UtxoSetHash is implemented as an index (subclass of BaseIndex)
and maintains data in LevelDB. It keeps the muhash for each block
in the database and also allows to search them by block hash or
height. It also maintains the global Muhash object which is being
modified as new blocks get added to the chain or as reorgs happen.

This commit also adds a serialization method to the Muhash object
to be able to persist it between restarts of the node.

Author: fjahr

src/Makefile.am

@@ -135,6 +135,7 @@ BITCOIN_CORE_H = \
   index/base.h \
   index/blockfilterindex.h \
   index/txindex.h \
+  index/utxosethash.h \
   indirectmap.h \
   init.h \
   interfaces/chain.h \
@@ -270,6 +271,7 @@ libbitcoin_server_a_SOURCES = \
   index/base.cpp \
   index/blockfilterindex.cpp \
   index/txindex.cpp \
+  index/utxosethash.cpp \
   interfaces/chain.cpp \
   interfaces/node.cpp \
   init.cpp \

src/crypto/muhash.h

@@ -10,6 +10,7 @@
 #endif
 
 #include <stdint.h>
+#include <serialize.h>
 
 struct Num3072 {
 #ifdef HAVE___INT128
@@ -47,6 +48,15 @@ class MuHash3072
 
     /* Finalize into a 384-byte hash. Does not change this object's value. */
     void Finalize(unsigned char* hash384) noexcept;
+
+    ADD_SERIALIZE_METHODS;
+
+    template <typename Stream, typename Operation>
+    inline void SerializationOp(Stream& s, Operation ser_action) {
+        for(int i = 0; i<data.LIMBS; i++) {
+            READWRITE(data.limbs[i]);
+        }
+    }
 };
 
 #endif // BITCOIN_CRYPTO_MUHASH_H