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.
Now returns no data for alarm and error enums when firmware is compiled for 128K versions of the STM32F1xx MCU.
This frees up some flash space for plugins etc.
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.
