vfs:  Add conveying method to socket_method_set

Returns non-zero if the socket's fd receive queue is non-empty.
vfs:  Add conveying() primitive
libc:  Add stropts.h
[NEW] vfs:  Add stream
Genie:  Use vfs::stream for paired sockets
Merge branches 'stropts', 'vfs-stream' and 'conveying' into pass-fds
Genie:  Override PairedSocket::IOCtl() to pass fds
Merge branch 'pass-fds'
vfs:  Fix null dereference in seteof() primitive