mdoc macro to mention packages in manpages

Hello!

It seems that the current manpages do not use a standard, uniform way to
mention a package/port name.

I'm not very skilled about mdoc(7), but after some `zgrep' in
/usr/share/man/man* (as suggested in par. `10.3.5. Important Macros' in
the Handbook), I found several different solutions. Descriptions are
from mdoc(7):

- `Pa' (``An absolute or relative file system path, or a file or directory
  name'')
- `Dv' (``Defined variables such as preprocessor constants, constant
  symbols, enumeration values, and so on'')
- `Sy' (``Request a boldface font'', but also: ``When none of the semantic
  macros fit, it is also adequate for syntax elements that have to be
  given or that appear verbatim'')
- `Sq' (``Encloses its arguments in `typewriter' single-quotes'')
- `Fa' (``Function argument or parameter''

Maybe there is no specific macro to show a package/port. `Pa' has probably
been more frequently used.

Which is the most correct macro to be used? (Not necessarily between the
ones above).

And should also the category of the package/port be shown (for example,
`devel/cloudabi-toolchain') or not?

Any suggestion is welcome.

Bye!

Rocky