Minor update to further eliminate the ole long slope deceleration issue. New update note!

- Added another way to further ensure the long slope deceleration issue
is eliminated. If the stepper rate change is too great near zero, the
stepper rate is adjusted at half increments to the end of travel,
creating a smooth transition. - If the new STEPPER_IDLE_LOCK_TIME is
set as zero, this delay is not compiled at compile-time. - NOTE: The
next update is likely going to be major, involving a full re-write of
the stepper.c program to integrate a simple way to apply pauses,
jogging, e-stop, and feedrate overrides. The interface should be
flexible enough to be easily modified for use with either hardware
switches or software commands. Coming soon.

stepper.c

@@ -86,7 +86,9 @@ void st_wake_up() {
 static void st_go_idle() {
   // Force stepper dwell to lock axes for a defined amount of time to ensure the axes come to a complete
   // stop and not drift from residual inertial forces at the end of the last movement.
-  _delay_ms(STEPPER_IDLE_LOCK_TIME);   
+  #if STEPPER_IDLE_LOCK_TIME
+    _delay_ms(STEPPER_IDLE_LOCK_TIME);   
+  #endif
   // Disable steppers by setting stepper disable
   STEPPERS_DISABLE_PORT |= (1<<STEPPERS_DISABLE_BIT);
   // Disable stepper driver interrupt
@@ -207,6 +209,8 @@ SIGNAL(TIMER1_COMPA_vect)
             // rounding errors that might leave steps hanging after the last trapezoid tick.
             if (trapezoid_adjusted_rate > current_block->rate_delta) {
               trapezoid_adjusted_rate -= current_block->rate_delta;
+            } else {
+              trapezoid_adjusted_rate >>= 1; // Bit shift divide by 2
             }
             if (trapezoid_adjusted_rate < current_block->final_rate) {
               // Reached final rate a little early. Cruise to end of block at final rate.