Previously accept() would copy the listener socket's cloexec and
non-blocking flag. With that fixed however TCPServer and LocalServer
now leak file descriptors into child processes and are blocking.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
(...and ASSERT_NOT_REACHED => VERIFY_NOT_REACHED)
Since all of these checks are done in release builds as well,
let's rename them to VERIFY to prevent confusion, as everyone is
used to assertions being compiled out in release.
We can introduce a new ASSERT macro that is specifically for debug
checks, but I'm doing this wholesale conversion first since we've
accumulated thousands of these already, and it's not immediately
obvious which ones are suitable for ASSERT.
SOCK_NONBLOCK is a linux-ism that serenity and linux support. For lagom
builds, we use ioctl/fcntl to get a non-blocking socket the old
fashioned way. Some file re-org unhid the fcntl.h dependency of TcpServer,
so add the header explicitly.
