[win32] Remove support for VS6
[win32] Remove support for VS6

Change-Id: I9bccf1f74ba603a7210b700092e81a210216412d
Reviewed-on: https://review.couchbase.org/c/sigar/+/166714
Tested-by: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Richard de Mellow <3b8534f7ae49c77465cd6f1b512f27ec39f3eddd@couchbase.com>

couchbase/sigar,couchbase/sigar