mongo-sync: Verify document sizes before inserting.
mongo-sync: Verify document sizes before inserting.

Since insert can split documents, rush through the whole lot of them
before doing anything else, to see if we can insert them at all.

If we find any that is bigger than the maximum insert size, bail out
with EMSGSIZE.

algernon/libmongo-client,algernon/libmongo-client,algernon/libmongo-client