This is required after https://github.com/cloudflare/quiche/pull/593
moved BoringSSL around slightly.
This also means that Go is not needed to build BoringSSL anymore (the
one provided by quiche anyway).
Closes#5691
To avoid an explosion of jobs, extend the existing CMake tests with
ngtcp2 and quiche support. macOS was previously moved to GitHub actions,
so the non-Linux case can be dropped.
Reported by the new script 'scripts/copyright.pl'. The script has a
regex whitelist for the files that don't need copyright headers.
Removed three (mostly usesless) README files from docs/
Closes#5141