buffer: track next_power_of_two changes to size_t.
collection: use 100 for default batchSize in aggregate.
cursor: be tolerant of non-64bit id field.
bulk: Handle upsert on MongoDB < 2.6 with non-objectid _id fields.

Server versions before 2.6 only return the 'upserted' field in an update
result when the upserted _id is an ObjectId. If the user provides any
other value for _id in the query spec, or update document (for a replace
operation) the upserted field is not returned. This causes invalid counts
for nUpserted in the Bulk API result set.

This fixes CDRIVER-372.
Release 0.96.2
build: post-release bump.
build: bump libbson
build: rpm build improvements.
build: bump libbson for alignment fixes.
Merge branch 'tengen-master'

Conflicts:
	src/libbson
	src/mongoc/mongoc-buffer.c