Use highest OpenCL C version (#1081)

* Set the highest supported OpenCL C version.

* Remove gDeviceLt20 variable - not used anymore.

* Fix formatting issues

test_conformance/generic_address_space/basic_tests.cpp

@@ -1,6 +1,6 @@
 //
 // Copyright (c) 2017 The Khronos Group Inc.
-// 
+//
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
@@ -39,7 +39,9 @@ public:
 
         const char *srcPtr = src.c_str();
 
-        if (create_single_kernel_helper_with_build_options(context, &program, &kernel, 1, &srcPtr, "testKernel", "-cl-std=CL2.0")) {
+        if (create_single_kernel_helper(context, &program, &kernel, 1, &srcPtr,
+                                        "testKernel"))
+        {
             log_error("create_single_kernel_helper failed");
             return -1;
         }