Log Message:
Update databases/mongo-c-driver to 1.7.0.

- CMake build now installs .pc files for programs that link to
  libmongoc using pkg-config.
- New CMake option ENABLE_STATIC can be ON, OFF, or AUTO (the default)
- Minimum required CMake version has been increased to 3.1.
- Support for wire compression.
  - Support for snappy and zlib. MongoDB 3.4 only supports snappy,
    while zlib support is expected in MongoDB 3.6.
  - New functions: mongoc_uri_get_compressors &
    mongoc_uri_set_compressors, to get and set compressor
    configuration on mongoc_uri_t
  - Added support for comma seperated "compressors" connection string
    option (e.g. mongodb://localhost/?compressors=snappy,zlib)
  - Added support for configuring zlib compression level in the
    connection string (e.g.
    mongodb://localhost/?compressors=zlib&zlibcompressionlevel=8)
- Now requires the use of CMake config files for libbson to build
  libmongoc with CMake
- Added pkg-config support for libressl.
- New function mongoc_uri_set_auth_mechanism to update the
  authentication mechanism of a mongoc_uri_t after it is created from
  a string.
- New function mongoc_bulk_operation_insert_with_opts provides
  immediate error checking.
- New function mongoc_uri_new_with_error provides a way to parse a
  connection string, and retrieve the failure reason, if any.
- Support for MongoDB Connection String specification
  - All connection string options are now represented by
    MONGOC_URI_xxx macros
  - Paths to Unix Domain Sockets must be url encoded
  - Repeated options now issue warnings
  - Special characters in username, password and other values must be
    url encoded
  - Unsupported connection string options now issue warnings
  - Boolean values can now be represented as true/yes/y/t/1 and
    false/no/n/f/0.
  - Case is now preserved in Unix domain paths.
- New function mongoc_cursor_error_document provides access to
  server's error reply if a query or command fails.
- New function mongoc_write_concern_is_default determines whether any
  write concern options have been set, and
  mongoc_read_concern_is_default checks if read concern options are set.
- mongoc_gridfs_find_one_with_opts optimized to use limit 1.