title: Trying to compile OpenCL 1.2 example
body: <p>System:</p>
  <p><em>Ryzen 1600, r9 270 (radeon driver), ubuntu 16.04</em></p>
  <p>I'm trying to get my compiler (gcc 5.4.1) to compile some C++ with OpenCL but can't get it to find the header files.</p>
  <p>test.cpp:</p>
  <pre><code>    #include &lt;CL/cl.hpp&gt;
      int main(){}
  </code></pre>
  <p>I run <em>g++ test.cpp -lOpenCL</em> but get <em>fatal error: CL/cl.hpp: No such file or directory</em>.</p>
  <p>For other people with the same issue on StackOverflow, the issue was libOpenCL was not installed. But I have, I installed all these packages:</p>
  <p><em>opencl-headers, ocl-icd-opencl-dev, ocl-icd-libopencl1, mesa-opencl-icd,  clinfo, libclc-dev, libclc-amdgcn, libclcr600</em> (searched 'opencl' in synaptic)</p>
  <p>And running &quot;locate libOpenCL&quot; gives many entries including &quot;/usr/local/lib/libOpenCL.so&quot; which should be picked up by the -lOpenCL flag??</p>
  <p><strong>clinfo gives:</strong></p>
  <pre><code>Number of platforms                               1
    Platform Name                                   Clover
    Platform Vendor                                 Mesa
    Platform Version                                OpenCL 1.1 Mesa 17.2.8
    Platform Profile                                FULL_PROFILE
    Platform Extensions                             cl_khr_icd
    Platform Extensions function suffix             MESA
  
    Platform Name                                   Clover
  Number of devices                                 1
    Device Name                                     AMD PITCAIRN (DRM 2.50.0 / 4.13.0-37-generic, LLVM 5.0.0)
    Device Vendor                                   AMD
    Device Vendor ID                                0x1002
    Device Version                                  OpenCL 1.1 Mesa 17.2.8
    Driver Version                                  17.2.8
    Device OpenCL C Version                         OpenCL C 1.1 
    Device Type                                     GPU
    Device Profile                                  FULL_PROFILE
    Max compute units                               20
    Max clock frequency                             955MHz
    Max work item dimensions                        3
    Max work item sizes                             256x256x256
    Max work group size                             256
    Preferred work group size multiple              64
    Preferred / native vector sizes                 
      char                                                16 / 16      
      short                                                8 / 8       
      int                                                  4 / 4       
      long                                                 2 / 2       
      half                                                 0 / 0        (n/a)
      float                                                4 / 4       
      double                                               2 / 2        (cl_khr_fp64)
    Half-precision Floating-point support           (n/a)
    Single-precision Floating-point support         (core)
      Denormals                                     No
      Infinity and NANs                             Yes
      Round to nearest                              Yes
      Round to zero                                 No
      Round to infinity                             No
      IEEE754-2008 fused multiply-add               No
      Support is emulated in software               No
      Correctly-rounded divide and sqrt operations  No
    Double-precision Floating-point support         (cl_khr_fp64)
      Denormals                                     Yes
      Infinity and NANs                             Yes
      Round to nearest                              Yes
      Round to zero                                 Yes
      Round to infinity                             Yes
      IEEE754-2008 fused multiply-add               Yes
      Support is emulated in software               No
      Correctly-rounded divide and sqrt operations  No
    Address bits                                    64, Little-Endian
    Global memory size                              2147483648 (2GiB)
    Error Correction support                        No
    Max memory allocation                           1503238553 (1.4GiB)
    Unified memory for Host and Device              No
    Minimum alignment for any data type             128 bytes
    Alignment of base address                       1024 bits (128 bytes)
    Global Memory cache type                        None
    Image support                                   No
    Local memory type                               Local
    Local memory size                               32768 (32KiB)
    Max constant buffer size                        1503238553 (1.4GiB)
    Max number of constant args                     16
    Max size of kernel argument                     1024
    Queue properties                                
      Out-of-order execution                        No
      Profiling                                     Yes
    Profiling timer resolution                      0ns
    Execution capabilities                          
      Run OpenCL kernels                            Yes
      Run native kernels                            No
    Device Available                                Yes
    Compiler Available                              Yes
    Device Extensions                               cl_khr_global_int32_base_atomics cl_khr_global_int32_extended_atomics cl_khr_local_int32_base_atomics cl_khr_local_int32_extended_atomics cl_khr_byte_addressable_store cl_khr_fp64
  
  NULL platform behavior
    clGetPlatformInfo(NULL, CL_PLATFORM_NAME, ...)  Clover
    clGetDeviceIDs(NULL, CL_DEVICE_TYPE_ALL, ...)   Success [MESA]
    clCreateContext(NULL, ...) [default]            Success [MESA]
    clCreateContextFromType(NULL, CL_DEVICE_TYPE_CPU)  No devices found in platform
    clCreateContextFromType(NULL, CL_DEVICE_TYPE_GPU)  Success (1)
      Platform Name                                 Clover
      Device Name                                   AMD PITCAIRN (DRM 2.50.0 / 4.13.0-37-generic, LLVM 5.0.0)
    clCreateContextFromType(NULL, CL_DEVICE_TYPE_ACCELERATOR)  No devices found in platform
    clCreateContextFromType(NULL, CL_DEVICE_TYPE_CUSTOM)  No devices found in platform
    clCreateContextFromType(NULL, CL_DEVICE_TYPE_ALL)  Success (1)
      Platform Name                                 Clover
      Device Name                                   AMD PITCAIRN (DRM 2.50.0 / 4.13.0-37-generic, LLVM 5.0.0)
  
  ICD loader properties
    ICD loader Name                                 OpenCL ICD Loader
    ICD loader Vendor                               OCL Icd free software
    ICD loader Version                              2.2.8
    ICD loader Profile                              OpenCL 1.2
          NOTE:   your OpenCL library declares to support OpenCL 1.2,
                  but it seems to support up to OpenCL 2.1 too.
  </code></pre>