These are identified by misc-include-cleaner.  I've filtered out those
that break builds.  Also, I'm staying away from llvm-config.h,
config.h, and Compiler.h, which likely cause platform- or
compiler-specific build failures.

Suggestion came via post-commit review feedback

This adds a new diagnostic group, -Wc++-keyword, which is off by default
and grouped under -Wc++-compat. The diagnostic catches use of C++
keywords in C code.

This change additionally fixes an issue with -Wreserved-identifier not
diagnosing use of reserved identifiers in function parameter lists in a
function declaration which is not a definition.

Fixes https://github.com/llvm/llvm-project/issues/21898

It would be nice to see what our users think about this change, as this
is something that WG21/EWG quite wants to fix a handful of questionable
issues with UB. Depending on the outcome of this after being committed,
we might instead suggest EWG undeprecate this, and require a bit of
'magic' from the lexer.

Additionally, this patch makes it so we emit this diagnostic ALSO in
cases where the literal name is reserved. It doesn't make sense to limit
that.

---------

Co-authored-by: Vlad Serebrennikov <serebrennikov.vladislav@gmail.com>

Enabling __ptr32 keyword to support in Clang for z/OS. It is represented
by addrspace(1) in LLVM IR. Unlike existing implementation, __ptr32 is
not mangled into symbol names for z/OS.

This is to fix the white-space formatting of the TokenKey enum

Reverts llvm/llvm-project#90574

This PR implement [P3034R1 Module Declarations Shouldn’t be
Macros](https://wg21.link/P3034R1), and refactor the convoluted state
machines in module name lexical analysis.

---------

Signed-off-by: yronglin <yronglin777@gmail.com>
Co-authored-by: Aaron Ballman <aaron@aaronballman.com>
Co-authored-by: cor3ntin <corentinjabot@gmail.com>

This commit implements the entirety of the now-accepted [N3017
-Preprocessor
Embed](https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3017.htm) and
its sister C++ paper [p1967](https://wg21.link/p1967). It implements
everything in the specification, and includes an implementation that
drastically improves the time it takes to embed data in specific
scenarios (the initialization of character type arrays). The mechanisms
used to do this are used under the "as-if" rule, and in general when the
system cannot detect it is initializing an array object in a variable
declaration, will generate EmbedExpr AST node which will be expanded by
AST consumers (CodeGen or constant expression evaluators) or expand
embed directive as a comma expression.

This reverts commit
https://github.com/llvm/llvm-project/commit/682d461d5a231cee54d65910e6341769419a67d7.

---------

Co-authored-by: The Phantom Derpstorm <phdofthehouse@gmail.com>
Co-authored-by: Aaron Ballman <aaron@aaronballman.com>
Co-authored-by: cor3ntin <corentinjabot@gmail.com>
Co-authored-by: H. Vetinari <h.vetinari@gmx.com>

Reverts llvm/llvm-project#68620

Introduce or expose a memory leak and UB, see llvm/llvm-project#68620