Adapt for llvm v21

[PP-EXT] Add docker build support

[PP-EXT] Support init_spec(Generalization, ptr)

[PP-EXT] Disable warnings for pointer type convertion between gen and spec

[PP-EXT] Remove debug output of generalization name

[PP-EXT] Add build-clang.sh

Запрос на слияние 'refactor-1' (#5) из refactor-1 в pp-extension-v21.1.8

[PP-EXT] Refactoring, part 1

[PP-EXT] Enhance typedefs usage. Fix warning for default nultimethod

[PP-EXT] Support typedefs for specializations

[PP-EXT] Add test pp-mm-default-eq0-perimeter.c

[PP-EXT] Add pp-mm-default-eq0.c to check_all.py

[PP-EXT] Add default handler for "= 0" in multimethods

create .gitverse/workflows/cpp.yaml

[PP-EXT] Refactor check_all.py

[PP-EXT] Fix check_all

[PP-EXT] Add test for gvinit

[PP-EXT] Make __pp_gvinit__ linkage LinkOnceODRLinkage

[PP-EXT] Remove __pp_ctor