Following the merge of libbson and mongo-c-driver repositories (CDRIVER-2416), it is necessary to review and update the installation documentation for both libbson and libmongoc. The update should account for the transition away from autotools to cmake, eliminate redundant documentation, incorporate unique items from libbson installation documentation into mongo-c-driver installation documentation. The files of interest for this effort are doc/installing.rst and src/libbson/doc/installing.rst.