Retire Internet 4 socklib variants and headers
- Retire defines and structs previously wrapped in COMPAT_INET4 in net/if.h; netinet/in.h; sys/socket.h; sys/sockio.h
- Update the documentation accordingly and point to the migration page to guide anyone still targetting Internet 4. Document Service_InternetStatus 9.
- Add a preprocessor check to socklib.h pointing at the migration page too
- Skip generating veneers for original Internet 4 forms of accept; recvfrom; recvmsg; sendmsg; getpeername; getsockname
- Remove COMPAT_INET4 predefine from unixlib and inetlib Makefiles
- Consolidate two socklib Makefiles into one