Add needed platform defined gaurds to compile with Arduino IDE

Also removed explicit platform HAL directory inclusion from platformio.ini to make sure these errors are caught by Travis in the future

Marlin/src/HAL/HAL_LPC1768/HardwareSerial.cpp

@@ -20,6 +20,8 @@
  *
  */
 
+#ifdef TARGET_LPC1768
+
 #include "../../../macros.h"
 #include "../HAL.h"
 #include "HardwareSerial.h"
@@ -634,3 +636,5 @@ void UART3_IRQHandler (void)
 #ifdef __cplusplus
 }
 #endif
+
+#endif // TARGET_LPC1768

Marlin/src/HAL/HAL_LPC1768/LPC1768_Servo.cpp

@@ -61,6 +61,7 @@
  *
  */
 
+#ifdef TARGET_LPC1768
 
 #if HAS_SERVOS
 
@@ -166,5 +167,5 @@
 
 #endif // HAS_SERVOS
 
-
+#endif // TARGET_LPC1768
 

Marlin/src/HAL/HAL_LPC1768/SoftwareSerial.cpp

@@ -29,6 +29,7 @@ The latest version of this library can always be found at
 http://arduiniana.org.
 */
 
+#ifdef TARGET_LPC1768
 
 //
 // Includes
@@ -396,3 +397,5 @@ int SoftwareSerial::peek()
   // Read from "head"
   return _receive_buffer[_receive_buffer_head];
 }
+
+#endif // TARGET_LPC1768

Marlin/src/HAL/HAL_LPC1768/WInterrupts.cpp

@@ -16,6 +16,8 @@
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
 
+#ifdef TARGET_LPC1768
+
 #include "../../../macros.h"
 #include "../HAL.h"
 #include "arduino.h"
@@ -222,3 +224,5 @@ return; //silences warning
 }
 }
 #endif
+
+#endif // TARGET_LPC1768