Provide IPv6 functions equivalent to those for IPv4.

[jrha]

e.g. ip6_to_long...

Came from discussion of quattor/aquilon#42.

[jrha]

A complication is that the largest integer type in Pan is a long which has the same characteristics as a Java long, i.e. a signed 64-bit integer (-9223372036854775808 to 9223372036854775807) which is far too small for IPv6's 128-bits or even a pair of 64-bit values (network, host) unless we also expose Java's methods for treating longs as unsigned.

[jrha]

Another possibility would be to expose BigInteger as a new data type.

[urbonegi]

Lot of IPv6 support was enabled and sync to upstream during last couple of months. This is one of the main tag for this piece of work:
https://github.com/quattor/aquilon/releases/tag/1.12.40-rc1
@jrha can this be closed?

[jrha]

@urbonegi - No, this issue is for support in the Pan compiler, not aquilon.

[jrha]

Part of #14.