* dirmngr/dns.h (dns_strsection, dns_strclass)
(dns_strtype): Change APIs.
* dirmngr/dns.c (dns_p_lines): Use __dst for dns_strsection.
(dns_rr_print): Use __dst for dns_strclass and dns_strtype.
(dns_trace_dump): Likewise.
(dns_ai_print): Use __dst for dns_strtype.
(dns_strsection): Add an argument __dst for storage.
(dns_strclass, dns_strtype): Likewise.
(parse_packet): Use __dst for dns_strsection.
(send_query): Use __dst for dns_strtype.
(isection): Use __dst for dns_strsection.
(iclass): Use __dst for dns_strclass.
(itype): Use __dst for dns_strtype.