Fix for a few -Wextra warnings.

Marlin/Marlin_main.cpp

@@ -1753,7 +1753,7 @@ void kill()
   SERIAL_ERRORLNPGM(MSG_ERR_KILLED);
   LCD_ALERTMESSAGEPGM(MSG_KILLED);
   suicide();
-  while(1); // Wait for reset
+  while(1) { /* Intentionally left empty */ } // Wait for reset
 }
 
 void Stop()

Marlin/Sd2Card.cpp

@@ -42,7 +42,7 @@ static void spiInit(uint8_t spiRate) {
 /** SPI receive a byte */
 static uint8_t spiRec() {
   SPDR = 0XFF;
-  while (!(SPSR & (1 << SPIF)));
+  while (!(SPSR & (1 << SPIF))) { /* Intentionally left empty */ }
   return SPDR;
 }
 //------------------------------------------------------------------------------
@@ -52,18 +52,18 @@ static inline __attribute__((always_inline))
   if (nbyte-- == 0) return;
   SPDR = 0XFF;
   for (uint16_t i = 0; i < nbyte; i++) {
-    while (!(SPSR & (1 << SPIF)));
+    while (!(SPSR & (1 << SPIF))) { /* Intentionally left empty */ }
     buf[i] = SPDR;
     SPDR = 0XFF;
   }
-  while (!(SPSR & (1 << SPIF)));
+  while (!(SPSR & (1 << SPIF))) { /* Intentionally left empty */ }
   buf[nbyte] = SPDR;
 }
 //------------------------------------------------------------------------------
 /** SPI send a byte */
 static void spiSend(uint8_t b) {
   SPDR = b;
-  while (!(SPSR & (1 << SPIF)));
+  while (!(SPSR & (1 << SPIF))) { /* Intentionally left empty */ }
 }
 //------------------------------------------------------------------------------
 /** SPI send block - only one call so force inline */
@@ -71,12 +71,12 @@ static inline __attribute__((always_inline))
   void spiSendBlock(uint8_t token, const uint8_t* buf) {
   SPDR = token;
   for (uint16_t i = 0; i < 512; i += 2) {
-    while (!(SPSR & (1 << SPIF)));
+    while (!(SPSR & (1 << SPIF))) { /* Intentionally left empty */ }
     SPDR = buf[i];
-    while (!(SPSR & (1 << SPIF)));
+    while (!(SPSR & (1 << SPIF))) { /* Intentionally left empty */ }
     SPDR = buf[i + 1];
   }
-  while (!(SPSR & (1 << SPIF)));
+  while (!(SPSR & (1 << SPIF))) { /* Intentionally left empty */ }
 }
 //------------------------------------------------------------------------------
 #else  // SOFTWARE_SPI
@@ -174,7 +174,7 @@ uint8_t Sd2Card::cardCommand(uint8_t cmd, uint32_t arg) {
   if (cmd == CMD12) spiRec();
 
   // wait for response
-  for (uint8_t i = 0; ((status_ = spiRec()) & 0X80) && i != 0XFF; i++);
+  for (uint8_t i = 0; ((status_ = spiRec()) & 0X80) && i != 0XFF; i++) { /* Intentionally left empty */ }
   return status_;
 }
 //------------------------------------------------------------------------------

Marlin/cardreader.cpp

@@ -246,7 +246,9 @@ void CardReader::openFile(char* name,bool read)
           return;
         }
         else
-          ;//SERIAL_ECHOLN("dive ok");
+        {
+          //SERIAL_ECHOLN("dive ok");
+        }
           
         curDir=&myDir; 
         dirname_start=dirname_end+1;
@@ -340,7 +342,9 @@ void CardReader::removeFile(char* name)
           return;
         }
         else
-          ;//SERIAL_ECHOLN("dive ok");
+        {
+          //SERIAL_ECHOLN("dive ok");
+        }
           
         curDir=&myDir; 
         dirname_start=dirname_end+1;