Fixed compilation warnings under Windows

platforms/reference/src/ReferenceKernels.cpp

@@ -619,7 +619,7 @@ public:
     void findCoefficients(double& x, double* coeff) const {
         int length = values.size();
         double scale = (length-1)/(max-min);
-        int index = std::floor((x-min)*scale);
+        int index = (int) std::floor((x-min)*scale);
         double points[4];
         points[0] = (index == 0 ? 2*values[0]-values[1] : values[index-1]);
         points[1] = values[index];

platforms/reference/src/SimTKReference/PME.cpp

@@ -242,7 +242,7 @@ pme_update_grid_index_and_fraction(pme_t    pme,
              *    (And, by adding 100.0 box lengths, we would lose a bit of numerical accuracy here!)
 			 */
 			t  = (atomCoordinates[i][d] / periodicBoxSize[d] + 1.0)*pme->ngrid[d];
-			ti = t;
+			ti = (int) t;
 
 			pme->particlefraction[i][d] = t - ti;
 			pme->particleindex[i][d]    = ti % pme->ngrid[d];