Remote DoS on maliciously crafted answer

[xypiie]

• buffer: don't bail out when request is bigger than buffer
  to prevent remote DoS by malicious DNS repsonses, don't bail out
  with assert(), but copy as much as possible.
  This will probably lead to incomplete response, but the error
  handling of ldns will take over and the process will not just be
  killed.
  Issue found by Maciej Musial, Robert Rozanski and Monika Walendzik.

• ldns_str2rdf_dname: check for successful mallocs
  ldns_str2rdf_dname() is calling ldns_rdf_new_frm_data() but was not
  checking the return value for valid allocated memory.
  This could cause NULL pointer derefs in following code.
  Correcting this and returning LDNS_STATUS_MEM_ERR on failed mallocs.

[wtoorop]

Thanks. 7d98a7c looks fine and I'd like to accept that one right away.
ec313f4 , I'd like to accept partly. We cannot simply change a function prototype, so I propose having a new version of ldns_buffer_write_at (perhaps ldns_buffer_write_available_at ), and I would like to keep the assert, but then within ldns_buffer_write... I'll do a suggestion.