do not compile some address families when not available

This fixes the following error while compiling libnl3 on CentOS5:

addr.c:1027: error: 'AF_RDS' undeclared here (not in a function)
addr.c:1033: error: 'AF_CAN' undeclared here (not in a function)
addr.c:1034: error: 'AF_TIPC' undeclared here (not in a function)
addr.c:1036: error: 'AF_IUCV' undeclared here (not in a function)
addr.c:1037: error: 'AF_RXRPC' undeclared here (not in a function)
addr.c:1038: error: 'AF_ISDN' undeclared here (not in a function)
addr.c:1039: error: 'AF_PHONET' undeclared here (not in a function)
make[2]: *** [addr.lo] Error 1

Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Thomas Graf <tgraf@suug.ch>