Auto-generated patch based on clang-tidy readability-identifier-naming.
Only some manual cleanup for `extern "C"` declarations and a GTest change was required.

I'm not sure if this cleanup is actually very useful. It cleans up clang-tidy findings to the number of warnings from clang-tidy should be lower.  Since it was easy to do and required only little cleanup I thought I'd upload it for discussion.

One pattern that keeps recurring: Test **matchers** are also supposed to start with a lowercase letter as per LLVM convention. However GTest naming convention for matchers start with upper case. I would propose to keep stay consistent with the GTest convention there. However that would imply a lot of `//NOLINT` throughout these files.

To re-product this patch run:
```
run-clang-tidy -checks="-*,readability-identifier-naming" -fix -format ./clang-tools-extra/clangd
```

To convert the macro names, I was using this script with some manual cleanup afterwards:
https://gist.github.com/ChristianKuehnel/a01cc4362b07c58281554ab46235a077

Differential Revision: https://reviews.llvm.org/D115634

gcc issues warnings on copy constructors that do not explicitly
initialize the base class.

- Update .clang-tidy to ignore parameters of main like functions for naming violations in clang and llvm directory

Summary: Every call to a main like function in llvm and clang lib violates the naming convention for parameters. This prevents clang-tidy warning on such breaches.

Reviewers: alexfh, hokein

Reviewed By: hokein

Subscribers: merge_guards_bot, aheejin, cfe-commits, llvm-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D73715

Summary:
Some tidy checks have too many hits in the codebase, making it hard to spot
other results from clang-tidy, therefore rendering the tool less useful.

Two checks were disabled:
  - misc-non-private-member-variable-in-classes in the whole LLVM monorepo,
    it is very common to have those in LLVM and the style guide does not forbid
    them.
  - readability-identifier-naming in the clang subtree. There are thousands of
    violations in 'Sema.h' alone.

Before the change, 'Sema.h' had >1000 tidy warnings, after the change the number
dropped to 3 warnings (unterminated namespace comments).

Reviewers: alexfh, hokein

Reviewed By: hokein

Subscribers: llvm-commits, cfe-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D57573

llvm-svn: 352862

repository (the same content as those in llvm/ and clang/).

llvm-svn: 352516

Summary: LLVM .clang_tidy seems to be more up-to-date.

Reviewers: alexfh, simark

Reviewed By: alexfh

Subscribers: simark, cfe-commits

Differential Revision: https://reviews.llvm.org/D44628

llvm-svn: 327984

llvm-svn: 266184

llvm-svn: 266182

llvm-svn: 220862

Reviewers: chandlerc, djasper, alexfh

Reviewed By: alexfh

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D5237

llvm-svn: 217366

clang-tidy.

Reviewers: chandlerc, djasper

Reviewed By: djasper

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D5236

llvm-svn: 217365