Log Message:
Update mongo-c-driver to 0.98.0.

Changes in 0.98.0:
- This release is primarily a bugfix release and stabilization effort as we
  approach 1.0 of the MongoDB C driver.
- This release requires 0.98.0 of Libbson for improvements to the memory
  management system. You can now setup custom memory allocators at the
  start of the process.

Changes in 0.96.4:
- build/mci.sh script for automatically building Debian packages, RPMs,
  and Solaris packaging based on the host operating system.
- Various libbson improvements, now depending on 0.8.4.
- Alignment fixes for Solaris Studio C compiler via libbson.
- Addition of mongoc_gridfs_remove_by_filename() for removing a file from
  gridfs by filename.
- client command functions can now take a fully qualified namespace.
- collections can now support names that indicate a command namespace.
- Commands will no longer fail if they do not contain an "ok" field.
- OP_QUERY will now set the slaveOk bit in the wire protocol if
  readPreferences are set to non-PRIMARY.
- Various documentation and build fixes.