Silence compiler warnings in ThreadPoolInterface.h.

unsupported/Eigen/CXX11/src/ThreadPool/ThreadPoolInterface.h

@@ -21,8 +21,8 @@ class ThreadPoolInterface {
 
   // Submits a closure to be run by threads in the range [start, end) in the
   // pool.
-  virtual void ScheduleWithHint(std::function<void()> fn, int start,
-                                int end) {
+  virtual void ScheduleWithHint(std::function<void()> fn, int /*start*/,
+                                int /*end*/) {
     // Just defer to Schedule in case sub-classes aren't interested in
     // overriding this functionality.
     Schedule(fn);