added upper boundary to block reward reduction to ensure 63 million coins maximum

src/main.cpp

@@ -1110,7 +1110,13 @@ int64 static GetBlockValue(int nHeight, int64 nFees)
 
     // Permantently reduce the number of mined coins to 10 after block 620000
     if(nHeight > 620000){
-	nSubsidy = 10 * COIN;
+        if(nHeight < 3756000){
+	    nSubsidy = 10 * COIN;
+        }
+	    else
+        {
+            nSubsidy = 0 * COIN;
+        }
     }