[clang] [OpenCL] Add missing OpenCL 3.0 features to OpenCLExtensions.def; revert header-only macros (PR #168016)

[Matt Arsenault via cfe-commits]

arsenm wrote:

> Hi, @wenju-he : After this patch, we are seeing a lot of OpenCL 2.0 conformance test failures due to undeclared functions/ __opencl_c_read_write_images is not being defined (was defined in opencl-c-base.h). Is there anything missing in the patch, or we are supposed to use alternative to define it? Thanks. cc: @arsenm

Didn't 9fd288e8866788d9defccccfcc75272eb27f54fe and 669683a036bf256e9cfba21bd2b70bafbf03be45 fix it? 

https://github.com/llvm/llvm-project/pull/168016