This legacy header appears to be unused. Removing its includes
avoids numerous warnings when compiling with musl libc:
/usr/include/sys/signal.h:1:2: warning: #warning redirecting incorrect #include <sys/signal.h> to <signal.h> [-Wcpp]
- Include arpa/inet.h to get hton* ntoh* functions.
- Use socklen_t instead of int.
- Try to define PF_INET to AF_INET if it doesn't exist.
Reported-by: Andy Tanenbaum <ast@cs.vu.nl>
