Cross-platform versions of msghdr, sendmsg, recvmsg, linger, and iovec
were provided based on findings from glibc, musl, and Microsoft's
documentation.
Implemented initial Reactor interface for epoll (linux) which wraps
around I/O reactor subsystems such as epoll, kqueue, select, etc. across
different platforms. The Reactor interface allows for driving async I/O
in Zig applications.
A test was added for the Reactor interface to drive a TCP
client/listener socket pair.
A greatest-common-subset of possible socket initialization flags (close
socket on exec syscalls, initialize socket to be non-blocking) were
implemented.
A test was added for using sendmsg/recvmsg syscalls across different
platforms for a TCP client/listener socket pair.
* `comptime const` is redundant
* don't use `extern enum`; specify a tag type.
`extern enum` is only when you need tags to alias. But aliasing tags
is a smell. I will be making a proposal shortly to remove `extern enum`
from the language.
* there is no such thing as `packed enum`.
* instead of `catch |_|`, omit the capture entirely.
* unused function definition with missing parameter name
* using `try` outside of a function or test
