Further planner improvements and misc minor bug fixes. Memory savings and increased buffer size.

- Update grbl version and settings version to automatically reset
eeprom. FYI, this will reset your grbl settings. - Saved
3*BLOCK_BUFFER_SIZE doubles in static memory by removing obsolete
variables: speed_x, speed_y, and speed_z. - Increased buffer size
conservatively to 18 from 16. (Probably can do 20). - Removed expensive!
modulo operator from block indexing function. Reduces significant
computational overhead. - Re-organized some sqrt() calls to be more
efficient during time critical planning cases, rather than non-time
critical. - Minor bug fix in planner max junction velocity logic. -
Simplified arc logic and removed need to multiply for CW or CCW
direction.

settings.c

@@ -3,7 +3,7 @@
   Part of Grbl
 
   Copyright (c) 2009-2011 Simen Svale Skogsrud
-  Modifications Copyright (c) 2011 Sungeun (Sonny) Jeon  
+  Copyright (c) 2011 Sungeun Jeon  
 
   Grbl is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
@@ -52,7 +52,7 @@ typedef struct {
 #define DEFAULT_RAPID_FEEDRATE 500.0 // in millimeters per minute
 #define DEFAULT_FEEDRATE 500.0
 #define DEFAULT_ACCELERATION (DEFAULT_FEEDRATE/10.0)
-#define DEFAULT_JUNCTION_DEVIATION 0.1
+#define DEFAULT_JUNCTION_DEVIATION 0.05
 #define DEFAULT_STEPPING_INVERT_MASK ((1<<X_STEP_BIT)|(1<<Y_STEP_BIT)|(1<<Z_STEP_BIT))
 
 void settings_reset() {