Garmin: StreetPilot c320 Firmware updates

Changes made from version 5.10 to 5.20:

* Improved route calculations with car pool lanes.

Changes made from version 4.80 to 5.10:

* Added via point support (After selecting Final Destination, select Via point from Where To? menu just like you would your Final Destination. Unit will prompt you if you wish to continue on to your Final Destination by way of your Via point. Select Yes).
* Improved address searches to allow for selecting which map to search on when multiple maps are available.
* Corrected a bug where the user could get stuck in the address search pages.
* Corrected a bug where some address searches would give back invalid results.
* Added ability to save waypoints from the Browse Map page.
* Improved city searches to search across all available maps.
* Improved the timing of voice guidance prompts.
* Added WebUpdater support for Voice Guidance updates.
* Corrected a bug where navigating on a roundabout could cause the unit to lock up."