Add and use <machine/rtems-bsd-kernel-space.h> and
<machine/rtems-bsd-user-space.h> similar to the libbsd to avoid command
line defines and defines scattered throught the code base.
Simplify cpukit/libnetworking/Makefile.am.
Update #3375.
It enabled promiscous mode or sets the multicast filter according
to the configuration and parameters to ioctl(SIOCSIFFLAGS),
ioctl(SIOCADDMULTI) and ioctl(SIOCDELMULTI).
On SIOCADDMULTI/SIOCDELMULTI requests the greth ioctl calls the
Ethernet helper functions ether_addmulti()/ether_delmulti() which
tells the greth driver when its required to update the MAC multicast
filtering.
The interface notifies support for multicast by setting IFF_MULTICAST.
The GRETH has two registers which contains a bit-mask of allowed MAC
addresses. The incomming MAC address is CRC:ed and the CRC is used as
an index into the bit-mask to determine to allow or drop the frame.
