[Linux] Read IPv6 stats with referring tags

[Target Tree]
5.5dev tree only

[Configuration]
--enable-ipv6

[Test Enviroment]
OpenSUSE 10.2 for i386
kernel: 2.6.20, libc: glibc-2.5, gcc: 4.1.2

====

The code which reads stats from /proc/net/snmp6 was developed
under assumption where no more stats would be added and
the order of stats is fixed. That's not true.

The attached proposal patch change the code to read the stats
with referring tags.