This includes deprecating std.c.*, which apparently was marked as
scheduled for deprecation in 2.068 but never actually deprecated (though
it looks like it was previously removed from the documentation build,
since it doesn't show up on dlang.org).
Previously, std.socket code assumed that MSG_NOSIGNAL existed on all platforms, which is not the case – std.c.osx.socket actually has a comment saying »Not defined in OS X, but we'll use them anyway«. This lead to Socket.send() raising SIGPIPE on OS X if the peer had already closed the connection.
With this commit, std.socket sets the SO_NOSIGPIPE socket option on systems that support it for the same effect as MSG_NOSIGNAL on Linux.
Strictly speaking, removing the NOSIGNAL SocketFlag is a breaking API change, but I do not think there is any code actually using it, as it has always been set implicitly by std.socket anyway.
* Transformed std.c.linux.* into wrappers around core.sys.posix modules where appropriate.
* Added std.c.osx as the OSX equivalent of std.c.linux.
* Added std.c.osx.socket for OSX-specific socket declarations not covered by the Posix spec.
* Altered all makefiles to zip, etc, the new std.c.osx package.
