Separated COINBASE_FLAGS out into main.h and made RPC getmemorypool return it

src/bitcoinrpc.cpp

@@ -1871,6 +1871,7 @@ Value getmemorypool(const Array& params, bool fHelp)
             "  \"previousblockhash\" : hash of current highest block\n"
             "  \"transactions\" : contents of non-coinbase transactions that should be included in the next block\n"
             "  \"coinbasevalue\" : maximum allowable input to coinbase transaction, including the generation award and transaction fees\n"
+            "  \"coinbaseflags\" : data that should be included in coinbase so support for new features can be judged\n"
             "  \"time\" : timestamp appropriate for next block\n"
             "  \"bits\" : compressed target of next block\n"
             "If [data] is specified, tries to solve the block and returns true if it was successful.");
@@ -1925,6 +1926,7 @@ Value getmemorypool(const Array& params, bool fHelp)
         result.push_back(Pair("previousblockhash", pblock->hashPrevBlock.GetHex()));
         result.push_back(Pair("transactions", transactions));
         result.push_back(Pair("coinbasevalue", (int64_t)pblock->vtx[0].vout[0].nValue));
+        result.push_back(Pair("coinbaseflags", HexStr(COINBASE_FLAGS.begin(), COINBASE_FLAGS.end())));
         result.push_back(Pair("time", (int64_t)pblock->nTime));
 
         union {

src/main.cpp

@@ -3130,12 +3130,7 @@ void IncrementExtraNonce(CBlock* pblock, CBlockIndex* pindexPrev, unsigned int&
         hashPrevBlock = pblock->hashPrevBlock;
     }
     ++nExtraNonce;
-    pblock->vtx[0].vin[0].scriptSig = CScript() << pblock->nTime << CBigNum(nExtraNonce);
+    pblock->vtx[0].vin[0].scriptSig = (CScript() << pblock->nTime << CBigNum(nExtraNonce)) + COINBASE_FLAGS;
-
-    // Put "/P2SH/" in the coinbase so everybody can tell when
-    // a majority of miners support it
-    const char* pszP2SH = "/P2SH/";
-    pblock->vtx[0].vin[0].scriptSig += CScript() << std::vector<unsigned char>(pszP2SH, pszP2SH+strlen(pszP2SH));
     assert(pblock->vtx[0].vin[0].scriptSig.size() <= 100);
 
     pblock->hashMerkleRoot = pblock->BuildMerkleTree();

src/main.h

@@ -49,6 +49,12 @@ static const int fHaveUPnP = false;
 #endif
 
 
+// Put "/P2SH/" in the coinbase so everybody can tell when
+// a majority of miners support it
+static const char* pszP2SH = "/P2SH/";
+static const CScript COINBASE_FLAGS = CScript() << std::vector<unsigned char>(pszP2SH, pszP2SH+strlen(pszP2SH));
+
+