Patch for ip6_sprintf(), please review

[Alfred Perlstein]

Hello,

The following patch seems appropriate to apply
to fix the kernel ip6_sprintf() function.

What it is doing is ensuring that when we
abbreviate addresses that the longest string
of zeros is shortend, not the first run of
zeros.

Our internal commit log is:
problem:
Unification of IPv6 address representation
fix:
recommended format of text representing an IPv6 address
is summarized as follows.

1. omit leading zeros

2. "::" used to their maximum extent whenever possible

3. "::" used where shortens address the most

4. "::" used in the former part in case of a tie breaker

5. do not shorten one 16 bit 0 field

6. use lower case

Present code in ip6_sprintf() is following rules 1,2,5,6.
Adding fix for following other rules also.For following
rules 3 and 4, finding out the index where to replace zero's
with '::' and using that index.
References:
http://tools.ietf.org/html/draft-ietf-6man-text-addr-representation-04.html


Diff is attached in text format.

-- 
- Alfred Perlstein
.- AMA, VMOA #5191, 03 vmax, 92 gs500, 85 ch250, 07 zx10
.- FreeBSD committer
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