scorch zap allocate govarint.U64Base128Encoder just once
scorch zap allocate govarint.U64Base128Encoder just once

Instead of allocating a govarint.U64Base128Encoder in the inner loop,
allocate it just once on the outside, as it appears that it's just a
thin wrapper around binary.PutUvarint().

steveyen/bleve,steveyen/bleve,blevesearch/bleve,blevesearch/bleve