Prefer linux_sockaddr over osockaddr, so the latter can go away.

Prefer linux_sockaddr over osockaddr, so the latter can go away.
sys_socket() supports SOCK_{CLOEXEC,NONBLOCK} now, so build on that.
doaccept() supports the non-inheriting-of-O_NONBLOCK, so build on that.
Merge compat_sys_{accept,send,recv}() into their only callers.
Lie a little and use struct sockaddr in the linux socket syscall args when
 it's a return argument to avoid a bunch a casts.
Delete many other unnecessary sockaddr casts

verified with a curl Linux binary