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/serial.h

@@ -36,16 +36,6 @@
 
 #define SERIAL_NO_DATA 0xff
 
-#ifdef ENABLE_XONXOFF
-  #define RX_BUFFER_FULL 96 // XOFF high watermark
-  #define RX_BUFFER_LOW 64 // XON low watermark
-  #define SEND_XOFF 1
-  #define SEND_XON 2
-  #define XOFF_SENT 3
-  #define XON_SENT 4
-  #define XOFF_CHAR 0x13
-  #define XON_CHAR 0x11
-#endif
 
 void serial_init();
 
@@ -58,7 +48,11 @@ uint8_t serial_read();
 // Reset and empty data in read buffer. Used by e-stop and reset.
 void serial_reset_read_buffer();
 
+// Returns the number of bytes available in the RX serial buffer.
+uint8_t serial_get_rx_buffer_available();
+
 // Returns the number of bytes used in the RX serial buffer.
+// NOTE: Deprecated. Not used unless classic status reports are enabled in config.h.
 uint8_t serial_get_rx_buffer_count();
 
 // Returns the number of bytes used in the TX serial buffer.