Fix #143 - SerialConsole::puts is broken in new build.

My dumb dumb!  Used the correct casting operator and actually tested
the UART serial path this time before committing.
Implement Johanns method of specifying segments for delta bots in segments per second.
Added a config delta_segments_per_second which defaults to 0, which is off
Modified mm_per_line_segment to turn off segmentation when set to 0, otherwise is exactly the same
If both mm_per_line_segment and delta_segments_per_second are set then delta_segments_per_second takes precedence
Implement Johanns method of specifying segments for delta bots in segments per second.
  Added a config delta_segments_per_second which defaults to 0, which is off
  Modified mm_per_line_segment to turn off segmentation when set to 0, otherwise is exactly the same
  If both mm_per_line_segment and delta_segments_per_second are set then delta_segments_per_second takes precedence
  Added example to rostock config which uses the delta_segments_per_second to match current Johanns Marlin/Delta
Merge pull request #144 from wolfmanjm/feature/delta-segmentation

Feature/delta segmentation
Looks pretty harmless, merging, thanks a lot for the feature !
Merge remote-tracking branch 'upstream/edge' into firmconfig