tables on pgbench man page look garbled

[Peter Eisentraut]

The tables "pgbench Operators" and "pgbench Functions" on the pgbench 
man page (the actual man page, not the HTML reference page) look pretty 
garbled.  Also, on macOS, man prints a warning that the page is 
invalidly formatted.  But the garbledness happens on Linux as well, for 
example.  Apparently, our custom table layout doesn't map properly to 
the man format.  But for example, the earlier table "pgbench Automatic 
Variables", which doesn't use the custom table layout, looks fine. 
Anyone feel like looking into this further?