DNS-SRV Support

[davidrg]

DNS-SRV support, a feature available in Kermit 95, is currently disabled in CKW as it relies on a feature of MIT Kerberos that was removed in 2018 (wshelper).

DNS SRV support will need to be reimplemented for modern windows systems - perhaps using DnsQuery_A/DnsQuery_W/DnsQuery_Utf8 (possibly not available on NT/9x)? Otherwise perhaps we can steal some code from MIT Kerberos - the license is compatible.

wshelper removed in this commit: krb5/krb5@76aaa78

The specific functions being used (based on unresolved external symbol errors from the linker when wshelper isn't available) are:

• res_search - this lives in src/util/wshelper/res_quer.c
• rdn_expand - this lives in src/util/wshelper/res_comp.c

The MIT Kerberos commit that stopped using wshelper for SRV and TXT lookups is: krb5/krb5@67de45e