GridFS chunk_new: Initialize with the amount of space needed
GridFS chunk_new: Initialize with the amount of space needed

This avoids automatically allocating about 1.5 x as much space as needed

mongodb/mongo-c-driver-legacy,mongodb/mongo-c-driver-legacy,mongodb/mongo-c-driver-legacy,HeliumProject/mongo-c,Elastica/mongo-c-driver-legacy,HeliumProject/mongo-c,Elastica/mongo-c-driver-legacy,Elastica/mongo-c-driver-legacy,mongodb/mongo-c-driver-legacy,Elastica/mongo-c-driver-legacy,HeliumProject/mongo-c,HeliumProject/mongo-c