ipv6: dont pollute rx.h with rx_addr.h

Change-Id: Ib62d46c4fdcbaf454778f4bc0428dbd09b87f846
ipv4: convert rxkad to rx_sockaddr

(Note: It would be better to introduce a new version of
rxi_getaddr() which returns an int and takes a memory address of a
struct rx_sockaddr to be filled.)

Change-Id: I9149a4d088ab7936819f5cbb19f3d2a025f2bd65
ipv6: rx_addr tweaks to pacify make libafs, mostly

still need to fix LINUX/rx_kcommon.c syntax errors

Change-Id: Ie27d84de71788bb230da7f7c34d8584c780f7574