Revert "emergency fix so ppl can download large # objects in json"

This reverts commit c692b54bfd79114c9bf89dea5eb8c9715947a011.
Revert "Revert "emergency fix so ppl can download large # objects in json""

This reverts commit aaa5b34126398e1ef9a406ca2e21b3de73d3665d.
fix cores in top tree with last commit. this one
speeds things up greatly. don't scan scoreinfo buf
for every docid we add to top tree if scoreinfobuf
has plenty of space. later we'll have to be more
clever about removing things from scoreinfobuf
if it comes down to that.