tools: Save superpages in the same batch, to make detection easier

tools: Save superpages in the same batch, to make detection easier

On the first time through (when pfns are mostly allocated on
the receiving side), try to keep superpages together in the same
batch by ending a batch early if we see the first page of a
potential superpage and there isn't enough room in the batch
for a full superpage.

Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com>
Committed-by: Ian Jackson <ian.jackson.citrix.com>