Record track point description in GPX log

[samco]

I have created a patch to include support for recording a description in a track point in the GPX log file. This can be used from an OSD button as follows:

<osd enabled="yes" type="button" x="-96" y="300" command="vehicle.log_gpx_desc=&quot;Mark&quot;" src="mark.xpm"/>

This is very handy when audio mapping for OpenStreetMap?, as visual marks in the GPX log will then closely correspond with the audio description for that mark in the audio log.

I've also created mark.svg and mark.xpm, maybe someone with more graphical design skills than I have (ie, none) can do better?

[kazer]

Applied in rev 2945. Thank you!