udp: No data will be carried along w/ connect

Pull the assertion into earlier place.
net: Remove unnecessary sosetport() in various pru_attachs

The so_port is set before the pru_attach is called; there is no need
to do it again.
inet: in_pcbsetlport_remote -> in_pcbbind_remote

This function may change inp_laddr, so 'bind' is is better than
'setlport'.
inpcb: Cache align inpcbinfo
inpcb: Remove inp_cpcbinfo, which serves no purpose now

It is always same as inp_pcbinfo.
libmagic: link against libz

Linking a program against the library without explicitly
stating `-lz' produced this output:

    /usr/lib/libmagic.so: undefined reference to `inflate'
    /usr/lib/libmagic.so: undefined reference to `inflateInit2_'
    /usr/lib/libmagic.so: undefined reference to `inflateEnd'