dot/profile: Use control sequences rather than overstriking in man pages.

dot/profile: Use control sequences rather than overstriking in man pages.

The traditional overstriking is ambiguous regarding `_^H_', which may be
underlined (italics) or bold.  Pages like less(1) typically guess based
on the surrounding context, but this seriously screws up some fiddly
cases which switch between bold and underlining exactly at the boundary
between a non-underscore and an underscore.

The main Groff documentation is fairly adamant that this is the default
behaviour, but the Debian `/etc/groff/{man,mdoc}.local' files override
this unless `GROFF_SGR' is set nonempty in the environment.  This is
mentioned in the `changelog.Debian' file and nowhere else.