Use highest OpenCL C version (#1081)

* Set the highest supported OpenCL C version.

* Remove gDeviceLt20 variable - not used anymore.

* Fix formatting issues

test_conformance/images/samplerlessReads/test_read_1D_buffer.cpp

@@ -22,7 +22,6 @@
     #include <setjmp.h>
 #endif
 
-extern bool gDeviceLt20;
 
 const char *read1DBufferKernelSourcePattern =
 "__kernel void sample_kernel( read_only image1d_buffer_t inputA, read_only image1d_t inputB, sampler_t sampler, __global int *results )\n"
@@ -244,7 +243,8 @@ int test_read_image_set_1D_buffer( cl_device_id device, cl_context context, cl_c
              readFormat );
 
     ptr = programSrc;
-    error = create_single_kernel_helper_with_build_options( context, &program, &kernel, 1, &ptr, "sample_kernel", gDeviceLt20 ? "" : "-cl-std=CL2.0" );
+    error = create_single_kernel_helper(context, &program, &kernel, 1, &ptr,
+                                        "sample_kernel");
     test_error( error, "Unable to create testing kernel" );
 
     if ( gTestSmallImages )