Replace toothLastMinusOneToothTime calculations with lastGap

[DeionSi]

toothLastMinusOneToothTime is only used to calculate the gap between the last two triggers/edges/teeth and this is done in quite a few places throughout the code. Use lastGap variable instead and set it to the almost always already calculated curGap.

All patterns have been tested for basic sync/rpm readings with the following exceptions: Jeep 2000 not in ardustim, untested Harley EVO not in ardustim, untested 36-2-1 not in ardustim, untested (but similar decoder 36-2-2-2 works) Mazda AU does not sync on master

Bench-tested 0.4.3d with Ardu-Stim: Basic Distributor gives ~0,65% loops/sec increase across the RPM range Missing Tooth 60-2 gives loops/sec increase of 0,8% at 1000RPM and 2,4% at 6000RPM.

4 bytes less memory but 66 bytes larger firmware.