[gpsd-users] Suggest a little tweak to the documentation.

[Peter da Silva]

gpsd.8 reads:

-n
    Don't wait for a client to connect before polling whatever GPS is
    associated with it. Some RS232 GPSes wait in a standby mode (drawing
    less power) when the host machine is not asserting DTR, and some
    cellphone and handheld embedded GPSes have similar behaviors. Accordingly,
    waiting for a watch request to open the device may save battery power.
    (This capability is rare in consumer-grade devices and nonexistent in USB
    GPSes which lack a DTR line.)

It would be useful to change that last comment:

(This capability is rare in consumer-grade devices and nonexistent in USB
GPSes which lack a DTR line.)

To note that some USB GPSes (like the Pharos iGPS-500, bundled with Microsoft
Streets and Trips) are actually serial devices under the hood and require "-n"
in applications like acting as an input to nptd.

Maybe the minimal change would be "...in _those_ USB GPSes which lack a DTR 
line."?

At least give users a bit more of a hint where to look.