Don't define min/max macros for win32

Change-Id: I3d2ce259c327ec9c4410909dff5c0cdc1e6409ee
Reviewed-on: http://review.couchbase.org/30706
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>