v1.1b: Tweaked Bf reports, jogging doc, saved another 160 bytes, minor bug fixes

- Increment to v1.1b due to status report tweak.

- Tweaked the buffer state status reports to show bytes and blocks
available, rather than in use. This does not require knowing the buffer
sizes beforehand. It’s implicit.

- Also, since buffer states are not used by most devs (after
inquiries), it is no longer enabled by default and a status mask option
was added for this.

- Fixed some typos and updated for the report tweak in the
documentation.

- Wrote a joystick implementation concept in the jogging markdown
document. Outlines how to get a low-latency feel to a joystick (and
other input devices).

- Removed XON/XOFF support. It’s not used by anyone because of its
inherent problems. Remains in older versions for reference.

- Added a compile option on how to handle the probe position during a
check mode.

- Fixed a jogging bug. If G93 is the modal state before a jogging
motion, the feed rate did not get calculated correctly. Fixed the issue.

- Refactored some code to save another 160+ bytes. Included an improved
float vector comparison macro and reducing a few large and repetitive
function calls.

- Fixed a probing bug (existing in v0.9 too) where the target positions
were not set correct and error handling was improper.

grbl/config.h

@@ -254,10 +254,10 @@
 // NOTE: This feature is new and experimental. Make sure the GUI you are using supports this mode.
 #define REPORT_GUI_MODE // Default enabled. Comment to disable.
 
-// The status report change for Grbl v1.0 and after also removed the ability to disable/enable data fields
-// from the report. This caused issues for GUI developers, who've had to manage several scenarios and
-// configurations. The increased efficiency of the new reporting style allows for all data fields to be
-// sent without potential performance issues.
+// The status report change for Grbl v1.0 and after also removed the ability to disable/enable most data
+// fields from the report. This caused issues for GUI developers, who've had to manage several scenarios
+// and configurations. The increased efficiency of the new reporting style allows for all data fields to 
+// be sent without potential performance issues.
 // NOTE: The options below are here only provide a way to disable certain data fields if a unique
 // situation demands it, but be aware GUIs may depend on this data. If disabled, it may not be compatible.
 #define REPORT_FIELD_BUFFER_STATE // Default enabled. Comment to disable.
@@ -453,16 +453,6 @@
 // #define RX_BUFFER_SIZE 128 // (1-254) Uncomment to override defaults in serial.h
 // #define TX_BUFFER_SIZE 90  // (1-254)
 
-// Toggles XON/XOFF software flow control for serial communications. Not officially supported
-// due to problems involving the Atmega8U2 USB-to-serial chips on current Arduinos. The firmware
-// on these chips do not support XON/XOFF flow control characters and the intermediate buffer
-// in the chips cause latency and overflow problems with standard terminal programs. However,
-// using specifically-programmed UI's to manage this latency problem has been confirmed to work.
-// As well as, older FTDI FT232RL-based Arduinos(Duemilanove) are known to work with standard
-// terminal programs since their firmware correctly manage these XON/XOFF characters. In any
-// case, please report any successes to grbl administrators!
-// #define ENABLE_XONXOFF // Default disabled. Uncomment to enable.
-
 // A simple software debouncing feature for hard limit switches. When enabled, the interrupt
 // monitoring the hard limit switch pins will enable the Arduino's watchdog timer to re-check
 // the limit pin state after a delay of about 32msec. This can help with CNC machines with
@@ -472,6 +462,10 @@
 // work well and are cheap to find) and wire in a low-pass circuit into each limit pin.
 // #define ENABLE_SOFTWARE_DEBOUNCE // Default disabled. Uncomment to enable.
 
+// Configures the position after a probing cycle during Grbl's check mode. Disabled sets
+// the position to the probe target, when enabled sets the position to the start position.
+// #define SET_CHECK_MODE_PROBE_TO_START // Default disabled. Uncomment to enable.
+
 // Force Grbl to check the state of the hard limit switches when the processor detects a pin
 // change inside the hard limit ISR routine. By default, Grbl will trigger the hard limits
 // alarm upon any pin change, since bouncing switches can cause a state check like this to