[$] Better guidance for database developers

At the inaugural Databasesmicroconference at the 2019 Linux Plumbers Conference (LPC), twodevelopers who work on rather different database systems had similarcomplaints about developing for Linux. Richard Hipp, creator of the SQLitedatabase, and Andres Freund from the PostgreSQL project both lamented thelack of definitive documentation on how to best use the kernel's I/O interfaces,especially for corner cases. Both of the sessions, along with others inthe microconference, pointed to a strong need for more interaction betweenuser-space and kernel developers.