Force explicit double -> int conversion for CFeeRate constructor

This resolves an issue where estimatesmartfee would return 999
sat/byte instead of 1000, due to floating point loss of precision

Thanks to sipa for suggesting is_integral.

src/policy/fees.cpp

@@ -714,7 +714,7 @@ CFeeRate CBlockPolicyEstimator::estimateRawFee(int confTarget, double successThr
     if (median < 0)
         return CFeeRate(0);
 
-    return CFeeRate(median);
+    return CFeeRate(llround(median));
 }
 
 unsigned int CBlockPolicyEstimator::HighestTargetTracked(FeeEstimateHorizon horizon) const
@@ -901,7 +901,7 @@ CFeeRate CBlockPolicyEstimator::estimateSmartFee(int confTarget, FeeCalculation
 
     if (median < 0) return CFeeRate(0); // error condition
 
-    return CFeeRate(median);
+    return CFeeRate(llround(median));
 }