Handle hostnames in fr_pton4/6

[spbnick]

Make fr_pton4/6 handle hostnames longer than the longest address +
prefix.

This fixes the issue where a long hostname would be rejected by e.g. radclient as an invalid IP address. E.g.:

$ radclient -x foofoof.barbarb.bazbazb.com auth testing123
radclient: Invalid IPv4 address string "foofoof.barbarb.bazbazb.com"

Whereas the expected response (produced after the fix) is:

radclient: Failed resolving "foofoof.barbarb.bazbazb.com" to IPv4 address: Name or service not known

[arr2036]

Just increase the buffer size to 256. This has already been changed in v4.0.x.

There's actually a 255 byte limit defined in RFC 1035 Section 2.3.4.

[spbnick]

Ah, I looked but failed to find that RFC. Updated, thanks, Arran.