Increased g-code parser line buffer. Added line overflow feedback.

- Increased g-code parser line buffer from 50 to 70 characters. Should
fix most all issues with long arc statements, provided that they are 8
digits(float) long only.

- Added a line buffer overflow feedback error to let the user know when
it encounters this problem. Resets the line whenever this occurs.
(Thanks @BHSPitMonkey!)

protocol.c

@@ -37,10 +37,16 @@ static uint8_t char_counter; // Last character counter in line variable.
 static uint8_t iscomment; // Comment/block delete flag for processor to ignore comment characters.
 
 
-void protocol_init() 
+static void protocol_reset_line_buffer()
 {
   char_counter = 0; // Reset line input
   iscomment = false;
+}
+
+
+void protocol_init() 
+{
+  protocol_reset_line_buffer();
   report_init_message(); // Welcome message   
   
   PINOUT_DDR &= ~(PINOUT_MASK); // Set as input pins
@@ -303,9 +309,8 @@ void protocol_process()
         // Empty or comment line. Skip block.
         report_status_message(STATUS_OK); // Send status message for syncing purposes.
       }
-      char_counter = 0; // Reset line buffer index
-      iscomment = false; // Reset comment flag
-      
+      protocol_reset_line_buffer();      
+    
     } else {
       if (iscomment) {
         // Throw away all comment characters
@@ -322,7 +327,9 @@ void protocol_process()
           // Enable comments flag and ignore all characters until ')' or EOL.
           iscomment = true;
         } else if (char_counter >= LINE_BUFFER_SIZE-1) {
-          // Throw away any characters beyond the end of the line buffer          
+          // Report line buffer overflow and reset
+          report_status_message(STATUS_OVERFLOW);
+          protocol_reset_line_buffer();
         } else if (c >= 'a' && c <= 'z') { // Upcase lowercase
           line[char_counter++] = c-'a'+'A';
         } else {