Fix IpAddress::toBulletMasked() for IP addresses with unmasked quadruplets with value...

Fix IpAddress::toBulletMasked() for IP addresses with unmasked quadruplets with value zero

Rebuild the IPv6 masking algorithm to a proper parser handling the quadruplets
one-by-one, instead of attempting to process the IP address using regular
expressions.

This patch fixes masking of IP addresses such as:

    2001:db8:1234:0:abcd::1234

Applying a /64 mask will transform the IP address into:

    2001:db8:1234::

Note how the explicit 0 block is elided as well.

Previously the bullet masking algorithm would transform this into:

    2001:db8:1234:••••:••••:••••:••••

Resulting in an IP address with just 7 quadruplets. Now it correctly returns:

    2001:db8:1234:0:••••:••••:••••:••••