Using the same test as in 7af97c0365d86ec851c56d2d3736be2cc281af29,
transmitted wire bytes drops from 135,531 to 133,071 (-1.81%), while
received drops from 21,073 to 14,775 (-30%).

Combined, both changes shave 13,914 bytes (-8.6%) off aggregate
bandwidth usage.

Make it configurable as compression hurts in some scenarios.