Add support for Rack::ContentLength middelware
Merge pull request #16793 from javan/comply_with_rack_content_length_middleware

Add support for Rack::ContentLength middelware
Ignore segfault build errors with 2.0.0 + mysql-ruby

Continuation of c9a43126c5e2c608ab3ff1be994bce69e815a144

:cry:
[guides] Use `match ..., via: :all` in the custom exceptions app [ci skip]

Using `get` results in an unexpected error page(returning empty body) for requests of other HTTP mehtods other than GET. Use `match ..., via:
:all` so the exceptions app can be more stable.
Merge pull request #16832 from yuki24/use-match-via-all-in-custom-exceptions-app

[guides] Use `match ..., via: :all` in the custom exceptions app [ci skip]