Remove special win32 include dir

This is provided through our toplevel platform/include/win32

Change-Id: Ib4ebbda17b44c708ac9f7397453d367b76c9215f
Reviewed-on: http://review.couchbase.org/34010
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>