Do the proper hack for the (Open)BSD getaddrinfo quirk.

Do the proper hack for the (Open)BSD getaddrinfo quirk.

From evutil.c:

   Some older BSDs (like OpenBSD up to 4.6) used to believe that
   giving a numeric port without giving an ai_socktype was verboten.
   We test for this so we can apply an appropriate workaround.  If it
   turns out that the bug is present, then:

    - If nodename==NULL and servname is numeric, we build an answer
      ourselves using evutil_getaddrinfo_common().

    - If nodename!=NULL and servname is numeric, then we set
      servname=NULL when calling getaddrinfo, and post-process the
      result to set the ports on it.

   We test for this bug at runtime, since otherwise we can't have the
   same binary run on multiple BSD versions.

svn:r1550