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 *
According to the Single UNIX Specification, Version 2 the <arpa/inet.h>
header may optionally include <netinet/in.h> and <inttypes.h>. This
helps with porting software like c-ray that expects this to be the case.