Fixed some compilation errors on OS X

platforms/opencl/src/OpenCLFFT3D.cpp

@@ -75,6 +75,7 @@ OpenCLFFT3D::OpenCLFFT3D(OpenCLContext& context, int xsize, int ysize, int zsize
             defines["PACKED_XSIZE"] = context.intToString(packedXSize);
             defines["PACKED_YSIZE"] = context.intToString(packedYSize);
             defines["PACKED_ZSIZE"] = context.intToString(packedZSize);
+            defines["M_PI"] = context.doubleToString(M_PI);
             cl::Program program = context.createProgram(OpenCLKernelSources::fftR2C, defines);
             packForwardKernel = cl::Kernel(program, "packForwardData");
             unpackForwardKernel = cl::Kernel(program, "unpackForwardData");

platforms/opencl/src/OpenCLKernels.cpp

@@ -1628,6 +1628,7 @@ void OpenCLCalcNonbondedForceKernel::initialize(const System& system, const Nonb
             pmeDefines["GRID_SIZE_Y"] = cl.intToString(gridSizeY);
             pmeDefines["GRID_SIZE_Z"] = cl.intToString(gridSizeZ);
             pmeDefines["EPSILON_FACTOR"] = cl.doubleToString(sqrt(ONE_4PI_EPS0));
+            pmeDefines["M_PI"] = cl.doubleToString(M_PI);
             bool deviceIsCpu = (cl.getDevice().getInfo<CL_DEVICE_TYPE>() == CL_DEVICE_TYPE_CPU);
             if (deviceIsCpu)
                 pmeDefines["DEVICE_IS_CPU"] = "1";