Additional build info in the $I printout.

- [new] Added total available planner buffer blocks (15 shown, but
there are 16. one is used by the ring buffer and to execute system
motions) and serial RX buffer bytes. This information is useful for
GUIs to setup and optimize their streaming protocols easily.

[doc] Updated the interface document to reflect the change.

doc/log/commit_log_v1.1.txt

@@ -1,3 +1,16 @@
+----------------
+Date: 2017-01-29
+Author: Sonny Jeon
+Subject: Tidying up parking override control implementation
+
+[new] Added a default configuration for the parking override control
+upon a reset or power-up. By default, parking is enabled, but this may
+be disabled via a config.h option.
+
+[fix] Parking override control should be checking if the command word
+is passed, rather than the value.
+
+
 ----------------
 Date: 2017-01-28
 Author: chamnit

doc/markdown/interface.md

@@ -408,14 +408,14 @@ Feedback messages provide non-critical information on what Grbl is doing, what i
   - `[VER:]` and `[OPT:]`: Indicates build info data from a `$I` user query. These build info messages are followed by an `ok` to confirm the `$I` was executed, like so:
  
       ```
-      [VER:v1.1d.20161014:Some string]
+      [VER:v1.1f.20170131:Some string]
-      [OPT:VL]
+      [OPT:VL,16,128]
       ok
       ```
       
   		- The first line `[VER:]` contains the build version and date.
       - A string may appear after the second `:` colon. It is a stored EEPROM string a user via a `$I=line` command or OEM can place there for personal use or tracking purposes.
-  		- The `[OPT:]` line follows immediately after and contains character codes for compile-time options that were either enabled or disabled. The codes are defined below and a CSV file is also provided for quick parsing. This is generally only used for quickly diagnosing firmware bugs or compatibility issues.
+  		- The `[OPT:]` line follows immediately after and contains character codes for compile-time options that were either enabled or disabled and two values separated by commas, which indicates the total usable planner blocks and serial RX buffer bytes, respectively. The codes are defined below and a CSV file is also provided for quick parsing. This is generally only used for quickly diagnosing firmware bugs or compatibility issues. 
 
 			| `OPT` Code | Setting Description, Units |
 |:-------------:|----|

grbl/grbl.h

@@ -23,7 +23,7 @@
 
 // Grbl versioning system
 #define GRBL_VERSION "1.1f"
-#define GRBL_VERSION_BUILD "20170129"
+#define GRBL_VERSION_BUILD "20170131"
 
 // Define standard libraries used by Grbl.
 #include <avr/io.h>

grbl/report.c

@@ -433,8 +433,12 @@ void report_build_info(char *line)
   #ifndef HOMING_INIT_LOCK
     serial_write('L');
   #endif
+
   // NOTE: Compiled values, like override increments/max/min values, may be added at some point later.
-  // These will likely have a comma delimiter to separate them.   
+  serial_write(',');
+  print_uint8_base10(BLOCK_BUFFER_SIZE-1);
+  serial_write(',');
+  print_uint8_base10(RX_BUFFER_SIZE);
 
   report_util_feedback_line_feed();
 }