Merge branch 'beta' into mergemaster

# Conflicts:
#	src/main.cpp

src/rpcmining.cpp

@@ -206,8 +206,13 @@ UniValue generate(const UniValue& params, bool fHelp)
     UniValue blockHashes(UniValue::VARR);
     unsigned int n = Params().EquihashN();
     unsigned int k = Params().EquihashK();
+    uint64_t lastTime = 0;
     while (nHeight < nHeightEnd)
     {
+        // Validation may fail if block generation is too fast
+        if (GetTime() == lastTime) MilliSleep(1001);
+        lastTime = GetTime();
+
 #ifdef ENABLE_WALLET
         std::unique_ptr<CBlockTemplate> pblocktemplate(CreateNewBlockWithKey(reservekey));
 #else