Summary

Small oversight from #1034, the underlying ColStr was not exported and could not be pre-allocated as needed.

proto.ColJSONStr {
	Str: proto.ColStr{
		Buf: make([]byte, 0, strSize * bufferSize),
		Pos: make([]proto.Position, 0, bufferSize),
	}
}

This PR exports Str so the above code is possible