It's only needed for using the static keyword. Since you removed those, clover builds it fine without it. Also removed the check since Mesa is considered IS_GENERIC now.
#pragma OPENCL EXTENSION cl_khr_byte_addressable_store : enable
#endif
-#ifdef cl_clang_storage_class_specifiers
-#pragma OPENCL EXTENSION cl_clang_storage_class_specifiers : enable
-#endif
-
/**
* vendor specific
*/
*/
#ifdef IS_AMD
-#ifndef cl_clang_storage_class_specifiers
#pragma OPENCL EXTENSION cl_amd_media_ops : enable
#pragma OPENCL EXTENSION cl_amd_media_ops2 : enable
#endif
-#endif
/**
* NV specific