Added tentative check for small values in split cycle calculation
Possible fix for overruns

After isolating crashes to the split cycle algorithm, initial tests do
not show outright failure in the same place as before. However, the
graphical glitch seems to have persisted.
Rearranged code slightly.

Purpose was to reduce duplicate status updates, but it doesn't seem to
affect the G-code preview glitch.
Fix for build issue without debug flags
Simple rearrangement to eliminate duplicate calls to toggle DIOs and status updates
Overhaul of tc runcycle to eliminate sqrt of small numbers
Replaced 'done' flag with 'splitting' for clarity
Refactored common code for cycle updates to reduce chance of bugs between parabolic and tangent blends
Stricter tolerances eliminate acceleration overages
Simplifications to final velocity and optimization calculations
Merge remote-tracking branch 'robell/circular-blend-arc-alpha' into ubc3-circular-blend-arc-alpha