Added experimental support for G66 (modal macro call) and G67 (end modal macro call).
Made axis letter to axis/motor assignment for axes ABCUVW freely changeable at compile time.
Fix for some G65 arguments being incorrectly validated for normal use (sign, range).
Added repeat support to G65 macro call via the optional L parameter word.
Changed default setting for ABC-axes to rotary.
Changed defaults for jerk settings to 10x acceleration settings.
Disabled jerk for jog, probe and spindle synchronized motion.
Added _active_probe system parameter, returns -1 if no probe inputs available.
Minor bug fix, G5.1 and G33.1 motion commands were not coverted to the correct string equivalent in $G output.
Some minor bug fixes such as incorrect error code returned for unknown $-commands and temporary incorrect position reporting on in-flight G92 offset changes.
Added lightweight JSON serializer outputting directly to file.
Fix for event handler sometimes called too early. Ref. issue #818.
For developers: added optional device filing system that can redirect file read/write to serial streams.
Added system parameter _tool_table_size, 0 if a tool table is not enabled.
Removed dependency on safety door input for parking settings: $41, $42, $56-$59, $392 and $393.
Removed strict dependency on spindle encoder input for spindle synced motion,
allows the use of the stepper spindle which has an implicit encoder.
Changed signature of vfs.on_mount() event.
Added grbl.on_cycle_start() event, fired on cycle start signal asserted or on cycle start real time command received.
Some low-level ioport improvements, added definition for virtual pins/ports.
Deprecated direct access to number of the different ioport ports in hal.port struct, use ioports_unclaimed() instead.
Removed IDLE state requirement for executing G65 macros, an error will no longer be returned and the macro will be run.
Added event handler for outputting welcome message on "native" USB connect for drivers that provides the linestate changed event.
Added support for LinuxCNC style (ABORT,<msg>) comment, requires expressions enabled. Terminates gcode program, outputs message and returns error 253.
Added PRM[<setting>] and PRM[<setting>,<bit>] functions to expressions, returns $-setting value or value of bit in integer type setting.
"hardened" flow control code, fixed bug in repeat...continue handling.
Changed signature of grbl.on_gcode_comment event, now returns status code.
Added named parameters for getting absolute (G53) position: _abs_x, abs_y, ...
Available when expression support is enabled.
Changed stepper enable HAL signature to allow current reduction when idle.
Added reference id to spindle registration in order to allow configuring default spindle, and possibly additional spindles, at compile time.
Added $384 setting for controlling G92 offset persistence.
Improved $help command output and handling.
Moved the optional tool table in non-volatile storage.
Added gcode parameter support and optional expression support.
