Add CashAddr Address Format

Ported from Bitcoin Unlimited, Bitcoin ABC

src/dstencode.h

@@ -0,0 +1,24 @@
+#ifndef BITCOIN_DSTENCODE_H
+#define BITCOIN_DSTENCODE_H
+
+// key.h and pubkey.h are not used here, but gcc doesn't want to instantiate
+// CTxDestination if types are unknown
+#include "key.h"
+#include "pubkey.h"
+#include "script/standard.h"
+#include <string>
+
+class Config;
+class CChainParams;
+
+std::string EncodeDestination(const CTxDestination &, const CChainParams &, const Config &);
+CTxDestination DecodeDestination(const std::string &addr, const CChainParams &);
+bool IsValidDestinationString(const std::string &addr, const CChainParams &params);
+
+// Temporary workaround. Don't rely on global state, pass all parameters in new
+// code.
+std::string EncodeDestination(const CTxDestination &);
+CTxDestination DecodeDestination(const std::string &addr);
+bool IsValidDestinationString(const std::string &addr);
+
+#endif // BITCOIN_DSTENCODE_H