Revert "dns: remove AI_V4MAPPED hint flag on FreeBSD"

This reverts commit 04bea9f.

PR-URL: nodejs#1555
Reviewed-By: Fedor Indutny <fedor@indutny.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

Author: cjihrig

lib/dns.js

@@ -127,11 +127,6 @@ exports.lookup = function lookup(hostname, options, callback) {
         hints !== (exports.ADDRCONFIG | exports.V4MAPPED)) {
       throw new TypeError('invalid argument: hints must use valid flags');
     }
-
-    // FIXME(indutny): V4MAPPED on FreeBSD results in EAI_BADFLAGS, because
-    // the libc does not support it
-    if (process.platform === 'freebsd' && family !== 6)
-      hints &= ~exports.V4MAPPED;
   } else {
     family = options >>> 0;
   }