Removed unused field yield_rng from mock_file_t.
Added third mention of starvation issues to comment about static_semaphore_t, instead of a mere two mentions.
Reintroduced comment about why sync_t works.
Updated comments and naming of snapshot node functions.
Adjusted comment about snapshot nodes and children a bit more.
Renamed semaphore_ to unwritten_changes_semaphore_.
Removed duplicate function find_matching_version.