libdane: add function dane_query_to_raw_tlsa

libdane: add function dane_query_to_raw_tlsa

This function converts a dane_query_t into the parameters needed for
dane_raw_tlsa() to make it easy to copy the results of the (synchronous)
lookup query from one process to another.

This code allocates an unnecessary extra NULL entry for dane_data_len
to avoid trying to malloc 0 bytes if q->data_entries is 0 (it is possible
for malloc/calloc to return NULL when requested to allocate 0 bytes).

Signed-off-by: Simon Arlott