Use the preinstalled cl.hpp if it's available

platforms/opencl/src/OpenCLContext.h

@@ -36,7 +36,22 @@
     // Prevent Windows from defining macros that interfere with other code.
     #define NOMINMAX
 #endif
-#include <cl.hpp>
+#if defined(__APPLE__) || defined(__MACOSX)
+    #include <OpenCL/opencl.h>
+#else
+    #include <CL/opencl.h>
+#endif
+#ifdef CL_VERSION_1_1
+    // OpenCL C++ bindings are included with OpenCL 1.1
+    #if defined(__APPLE__) || defined(__MACOSX)
+        #include <OpenCL/cl.hpp>
+    #else
+        #include <CL/cl.hpp>
+    #endif
+#else
+    // OpenCL C++ bindings are not included with OpenCL 1.0 so use a local copy.
+    #include <cl.hpp>
+#endif
 #include "openmm/internal/windowsExport.h"
 #include "OpenCLPlatform.h"