Changes

Fix flang tests after MLIR changes on the handling of declarative assembly

[clangd] Add desugared type to hover

Add desugared type to hover when the desugared type and the pretty-printed type are different.

```c++
template<typename T>
struct TestHover {
  using Type = T;
};

int main() {
  TestHover<int>::Type a;
}
```

```
variable a

Type: TestHover<int>::Type (aka int)
```

Reviewed By: sammccall

Differential Revision: https://reviews.llvm.org/D114522

[C++20] [Module] Support extern C/C++ semantics

According to [module.unit]p7.2.3, a declaration within a linkage-specification
should be attached to the global module.
This let user to forward declare types across modules.

Reviewed by: rsmith, aaron.ballman

Differential Revision: https://reviews.llvm.org/D110215

[NFC][lsan] Clang-format lsan_common.cpp

[NFC][lsan] Move method implementation up

[C++20] [Modules] Namespace Declaration shouldn't have module linkage

According to [basic.namespace.general]/p2, a namespace declaration
shouldn't have a module linkage.
> A namespace is never attached to a named module and never has a name
> with module linkage.

Without this patch, the compiler would crash for the test in assertion
enabled build due to inconsistent linkage for redeclaration for
namespaces.

Reviewed by: rsmith

Differential Revision: https://reviews.llvm.org/D115132

Build MLIR with -Werror=mismatched-tags (NFC)

This is a defensive action to catch at build time on Linux failures that
may happen only on Windows otherwise.

Differential Revision: https://reviews.llvm.org/D115316

Adjust "end namespace" comment in MLIR to match new agree'd coding style

See D115115 and this mailing list discussion:
https://lists.llvm.org/pipermail/llvm-dev/2021-December/154199.html

Differential Revision: https://reviews.llvm.org/D115309

[clangd] Make a.k.a printing configurable.

Currently, a.k.a printing is closed by default.

Reviewed By: sammccall, kadircet

Differential Revision: https://reviews.llvm.org/D114665

[NFC] Fix C++20 module test in PPC and warning

[NFC][asan] Remove -std=c++20 from test

Fails after D110215
with errors like
/usr/include/x86_64-linux-gnu/sys/types.h:33:9: error: unknown type name '__u_char'
typedef __u_char u_char;

[lsan] Replace atomic_store/atomic_load with atomic_fetch_add