The old code uses errno as the primary indicator for success or
failure. This is wrong because errno is only set for specific
combinations of the status return value and the h_errno variable.
The address family splitting via format_ai_family made unpredictable
the place where the canonname field was printed. This commit adjusts
the implementation so that the ai_flags is checked for consistency
across the list, and ai_canonname must only be present on the first
list element.
Tests for AI_CANONNAME are added to resolv/tst-resolv-basic.
This bug did not affect name resolution because those functions
indirectly call ns_name_pack with a buffer which is always larger
than the generated query packet, even in the case of the
longest-possible domain name.
