#567 bugs in DNS EBL parser

[Henning Westerholt]

Reported from Andrei:

[...]

BTW: there seem to be 2 small bugs in the k code:

dns_ebl_parser(...):

1.
len = *rdata;
^^^^^^^^^^^^ this is the position and not the len
if (rdata + 1 + len >= end)
^^^^^^^^^^^^^^^^^^^^^^^^^^ len being the position this is useless
it should be something like:
if (((rdata+4)>end)||((rdata+1+1+rdata[1]+2)>end)) goto error;
(4 being the minimum size for an ebl and the other expression
being ebl with minimum apex)

2.
ebl->apex_len=dn_expand(msg, end, rdata, ebl->apex, MAX_DNS_NAME-1);
^^^^^^^^^ dn_expand returns the compressed len so this should
be replaced by ebl->apex_len=strlen(ebl->apex).