Latest upstream commits, mostly

Marlin/planner.cpp

@@ -67,7 +67,7 @@
 //===========================================================================
 
 unsigned long minsegmenttime;
-float max_feedrate[NUM_AXIS]; // set the max speeds
+float max_feedrate[NUM_AXIS]; // Max speeds in mm per minute
 float axis_steps_per_unit[NUM_AXIS];
 unsigned long max_acceleration_units_per_sq_second[NUM_AXIS]; // Use M201 to override by software
 float minimumfeedrate;