Pull requests/graph c c and maybe 294

This should maybe also fix #294 - I can't get my APM Planner to crash when loading that log, but there are definitely some funky lines in there.

This pull request has additional error checks when scanning the numbers on a line, and it also rejects 'NaN' and 'INF' as numbers.

Futhermore, it scans the floats as doubles, which allow the graphing of Latitude and Longitude.