Merge pull request #2569 from z-gong/vvdrude

fix performance issue when use Drude force with velocity-verlet integrator

plugins/drude/openmmapi/include/openmm/internal/DrudeForceImpl.h

@@ -55,7 +55,7 @@ public:
     const DrudeForce& getOwner() const {
         return owner;
     }
-    void updateContextState(ContextImpl& context) {
+    void updateContextState(ContextImpl& context, bool& forcesInvalid) {
         // This force field doesn't update the state directly.
     }
     double calcForcesAndEnergy(ContextImpl& context, bool includeForces, bool includeEnergy, int groups);