Miscellaneous macros
--------------------
The default indentation is 7.2n for all output devices except for
`grohtml' which ignores indentation.
- Macro: .DT
Set tabs every 0.5 inches. Since this macro is always called
during a `TH' request, it makes sense to call it only if the tab
positions have been changed.
- Macro: .PD [nnn]
Adjust the empty space before a new paragraph (or section). The
optional argument gives the amount of space (default unit is `v');
without parameter, the value is reset to its default value (1 line
for tty devices, 0.4v otherwise).
This affects the macros `SH', `SS', `TP', `LP' (as well as `PP' and
`P'), `IP', and `HP'.