Update order.xml
[System] Fix parsing of IPv6 addresses (bug #18574)

From Dick Porter:

The IPv6 address parser misses some syntax errors, and can become confused by
addresses that at first glance look IPv4 compatible.  The attach patch contains
the following fixes:

Don't fail to parse an address if we mistakenly thought it was IPv4 compatible
or mapped, just treat it as IPv6.

Fix IPv4-compatible and mapped address formatting in ToString().

Fix parsing of colons - specifically occurrences of ':::'.

Make sure blocks of digits are no longer than 4 characters.

Add some more parsing tests to Mono's NUnit test suite.

Add a NUnit test for bogus IPv6 addresses.