Merge r1478905:

Make sure apr_sockaddr_info_get() returns an error if
- getaddrinfo() returned only useless entries
- getaddrinfo() returned EAI_SYSTEM but errno == 0
- gethostbyname() returns no error but an empty address list

Submitted by:  Jan Kaluža <jkaluza redhat com>, Stefan Fritsch


git-svn-id: https://svn.apache.org/repos/asf/apr/apr/branches/1.5.x@1478909 13f79535-47bb-0310-9956-ffa450edef68