CCBC-1234: Fixed SRV resolution to work with large record sizes.
CCBC-1234: Fixed SRV resolution to work with large record sizes.

Motivation
----------
In some cases, the answer records exceed the default answer buffer
size causing SRV lookups to fail on otherwise correctly configured
clusters.  This specifically occured with Couchbase Cloud.

Changes
-------
Adjusted DNS default answer buffer size to 4096 instead of the
default of 512.  This should allow ~40 node clusters rather than
being limited to the existing 5.

Change-Id: I284e314babd1835e9f8109749347af39d5e62034
Reviewed-on: http://review.couchbase.org/c/libcouchbase/+/128241
Tested-by: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Sergey Avseyev <87f6d5e4fd3644c3c20800cde7fd3ad1569370b3@gmail.com>

kojiromike/libcouchbase,couchbase/libcouchbase,kojiromike/libcouchbase,couchbase/libcouchbase,couchbase/libcouchbase,kojiromike/libcouchbase,couchbase/libcouchbase,couchbase/libcouchbase,couchbase/libcouchbase,couchbase/libcouchbase,kojiromike/libcouchbase