Various MSVC build issues:

  sqrt of an integer is ambiguous
  methods declared to return a value must return a value

platforms/reference/src/SimTKReference/ReferenceCMAPTorsionIxn.cpp

@@ -52,7 +52,7 @@ ReferenceCMAPTorsionIxn::ReferenceCMAPTorsionIxn(const vector<vector<vector<Real
    --------------------------------------------------------------------------------------- */
 
 void ReferenceCMAPTorsionIxn::calculateIxn(RealOpenMM** atomCoordinates, RealOpenMM** forces, RealOpenMM* totalEnergy) const {
-    for (int i = 0; i < torsionMaps.size(); i++)
+    for (unsigned int i = 0; i < torsionMaps.size(); i++)
         calculateOneIxn(i, atomCoordinates, forces, totalEnergy);
 }
 
@@ -113,7 +113,7 @@ void ReferenceCMAPTorsionIxn::calculateOneIxn(int index, RealOpenMM** atomCoordi
 
     // Identify which patch this is in.
 
-    int size = (int) SQRT(coeff[map].size());
+    int size = (int) SQRT(double(coeff[map].size()));
     RealOpenMM delta = 2*M_PI/size;
     int s = (int) (angleA/delta);
     int t = (int) (angleB/delta);
@@ -190,4 +190,5 @@ void ReferenceCMAPTorsionIxn::calculateOneIxn(int index, RealOpenMM** atomCoordi
 
 int ReferenceCMAPTorsionIxn::calculateBondIxn(int* atomIndices, RealOpenMM** atomCoordinates,
      RealOpenMM* parameters, RealOpenMM** forces, RealOpenMM* energyByBond, RealOpenMM* energyByAtom) const {
+         return 0; // but it must return a value to avoid MSVC compile error
 }