Replace cache_size with cache-size -- #2205
Made snapshot_nodes_by_block_id_ an std::map.
Use a boost::ptr_map to make code compile on old GCCs
Fix a leak/crash issue.
Merge branch 'daniel_2213' into v1.12.x
Merge branch 'daniel_2213' into next
Replaced a std::abs with ternary operator.

This gets things compiling on OS X.  (Dropping the std:: would be bad,
because we would not want to call some wrong stdlib.h abs by accident.)
Merge branch 'michel_2205_conf' into next
Replace cache_size with cache-size -- #2205
Merge branch 'sam_2217' into next
Merge branch 'next' of github.com:rethinkdb/rethinkdb into next
Merge branch 'v1.12.x' into next
Merge branch 'next' into sam_803_store