fahrenheit curve axes

Leftover from #793:

19 curves/tables have autotemp xBins against a hardcoded Celsius xAxis — e.g. cltFuelCorrCurve at :459 with xAxis = -40, 120, 9, bins cltFuelCorrBins. In °F mode the bin values render as °F on a −40..120 axis. That's pre-existing breakage from the original autotemp work, but the changelog entry ("all temperature gauges, datalogs, sensor adjustments, and thermistor calibration points display in °F") reads as if the feature is done, and it isn't. A @@tempgauge-style directive would cover both cases with one mechanism.

Start by locating cltFuelCorrCurve around line 459 and inspect the other autotemp xBins paired with hardcoded Celsius xAxis values. Compare the existing @@tempgauge-style directive and the related work in #793. Done means all 19 curves/tables render Fahrenheit bins against Fahrenheit axes without breaking Celsius mode.

Written by the indexing model from the issue text.