[SYCL] Enable Open CL types required for implementing the SYCL headers.

[erichkeane]

Summary

This patch implements a few of the OpenCL types for SYCL, however
doesn't bother handling semantic analysis as these are not intended to
be used anywhere but in the SYCL implementation.

Signed-off-by: Erich Keane <[e-mail]>

[erichkeane]

@bader : Is this what you meant? Feel free to add any reviewers you want for this. Note it is still dependent on D71016.

[bader]

In D77220#1954909, @erichkeane wrote:

@bader : Is this what you meant? Feel free to add any reviewers you want for this. Note it is still dependent on D71016.

Thanks! I'll add more reviewers.

[keryell]

clang/lib/Sema/SemaSYCL.cpp

357

Curious. What is the purpose?

426

Can it be const?
Can the data structure be partially shared with the one from the previous function?

[erichkeane]

clang/lib/Sema/SemaSYCL.cpp

357

Ah, this is a fix that should actually be in the parent commit: https://reviews.llvm.org/D71016

Since that one was put up for review, the implicit conversion here was removed. I likely forgot to 'git' this out of this and into the cherry pick of the parent revision in my repo. I'll 'remove' it from this patch.

426

It can absolutely be const (change made in the incoming patch), but I don't see a way to combine the two without making matchQualifiedTypeName awkward.

[Anastasia]

Seems reasonable from the OpenCL side.