As captured in issue #108044, HLSL 202x is the target language mode for
conformance for Clang. Earlier language modes will be a best effort and
prioritized after 2020x. To make this easier and reduce our testing
complexity we want to make 202x the default language mode now, and align
all earlier modes to match 202x (except where we explicitly deviate).
This change has the following concrete changes:
* All older language modes gain `CPlusPlus11` as a base
* The default language mode for HLSL sources is changed to 202x
* A few test cases are updated to resolve differences in generated
diagnostics.
Second to last change for #108044
HLSL does not support pointers or references. This change generates
errors in sema for generating pointer, and reference types as well as
common operators (address-of, dereference, arrow), which are used with
pointers and are unsupported in HLSL.
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D123167
