ip6addr_aton allows invalid IPv6 address strings

[wskellenger-intrepid]

I've added two test cases, both of which produce a true (valid IP address) response by aton(). Expected result is false (invalid IP address).

  const char *shortened_ipv6_addr_unexpected_char = "::FFFF:D4CC:65DZ";
  const char *shortened_ipv6_addr_invalid = "::GGGGGGGG";

I'm not sure why, but ip6addr_aton will check for invalid characters and then continue on. My solution was to add a return 0 in these cases, but I'm not sure if this is a robust solution or will cause more problems. All tests pass with this solution.

Update, also found the following failing test case and fixed it:

  const char *ipv6_block_too_long = "1234:5678:9aBc:acDef:1122:3344:5566:7788";

Update, found more problems, added tests and fixed.

• trailing single colon
• adding zero compression in an address that is already fully defined