Add settxfee RPC, to permit setting default TX fee at runtime.

src/rpc.cpp

@@ -465,6 +465,22 @@ Value getaddressesbyaccount(const Array& params, bool fHelp)
     return ret;
 }
 
+Value settxfee(const Array& params, bool fHelp)
+{
+    if (fHelp || params.size() < 1 || params.size() > 1)
+        throw runtime_error(
+            "settxfee <amount>\n"
+            "<amount> is a real and is rounded to the nearest 0.00000001");
+
+    // Amount
+    int64 nAmount = 0;
+    if (params[0].get_real() != 0.0)
+        nAmount = AmountFromValue(params[0]);        // rejects 0.0 amounts
+
+    nTransactionFee = nAmount;
+    return true;
+}
+
 Value sendtoaddress(const Array& params, bool fHelp)
 {
     if (fHelp || params.size() < 2 || params.size() > 4)
@@ -1441,6 +1457,7 @@ pair<string, rpcfn_type> pCallTable[] =
     make_pair("listtransactions",      &listtransactions),
     make_pair("getwork",               &getwork),
     make_pair("listaccounts",          &listaccounts),
+    make_pair("settxfee",              &settxfee),
 };
 map<string, rpcfn_type> mapCallTable(pCallTable, pCallTable + sizeof(pCallTable)/sizeof(pCallTable[0]));
 
@@ -2074,6 +2091,7 @@ int CommandLineRPC(int argc, char *argv[])
         if (strMethod == "setgenerate"            && n > 0) ConvertTo<bool>(params[0]);
         if (strMethod == "setgenerate"            && n > 1) ConvertTo<boost::int64_t>(params[1]);
         if (strMethod == "sendtoaddress"          && n > 1) ConvertTo<double>(params[1]);
+        if (strMethod == "settxfee"               && n > 0) ConvertTo<double>(params[0]);
         if (strMethod == "getamountreceived"      && n > 1) ConvertTo<boost::int64_t>(params[1]); // deprecated
         if (strMethod == "getreceivedbyaddress"   && n > 1) ConvertTo<boost::int64_t>(params[1]);
         if (strMethod == "getreceivedbyaccount"   && n > 1) ConvertTo<boost::int64_t>(params[1]);