renamed protocol methods to reflect the new module name

doc/structure.txt

@@ -3,10 +3,10 @@ The general structure of Grbl
 
 The main processing stack:
 
-'serial_protocol' : Accepts command lines from the serial port and passes them to 'gcode' for execution.
+'protocol' : Accepts command lines from the serial port and passes them to 'gcode' for execution.
                     Provides status responses for each command.
                   
-'gcode'           : Recieves gcode from 'serial_protocol', parses it according to the current state
+'gcode'           : Recieves gcode from 'protocol', parses it according to the current state
                     of the parser and issues commands via '..._control' modules
                   
 'spindle_control' : Commands for controlling the spindle.

main.c

@@ -37,7 +37,7 @@
 
 int main(void)
 {
-  sp_init();        
+  protocol_init();        
   settings_init();  
   plan_init();      
   st_init();        
@@ -46,7 +46,7 @@ int main(void)
                     
   for(;;){
     sleep_mode(); // Wait for it ...
-    sp_process(); // ... process the serial protocol
+    protocol_process(); // ... process the serial protocol
   }
   return 0;   /* never reached */
 }

protocol.c

@@ -51,14 +51,14 @@ void status_message(int status_code) {
   }
 }
 
-void sp_init() 
+void protocol_init() 
 {
   beginSerial(BAUD_RATE);  
   printPgmString(PSTR("\r\nGrbl " GRBL_VERSION));
   printPgmString(PSTR("\r\n"));  
 }
 
-void sp_process()
+void protocol_process()
 {
   char c;
   while((c = serialRead()) != -1) 

protocol.h

@@ -21,10 +21,10 @@
 #define serial_h
 
 // Initialize the serial protocol
-void sp_init();
+void protocol_init();
 
 // Read command lines from the serial port and execute them as they
 // come in. Blocks until the serial buffer is emptied. 
-void sp_process();
+void protocol_process();
 
 #endif