[common] Make Serial RX buffer size configurable, increase default to 256 bytes (#313)

* Make Serial RX buffer configurable and set default to 256 bytes

* Replace RingBuffer by SerialRingBuffer

cores/common/arduino/libraries/api/Serial/Serial.h

@@ -8,6 +8,8 @@
 
 using namespace arduino;
 
+typedef RingBufferN<LT_SERIAL_BUFFER_SIZE> SerialRingBuffer;
+
 class SerialClass : public HardwareSerial {
   private:
 	uint32_t port;
@@ -18,7 +20,7 @@ class SerialClass : public HardwareSerial {
 	void *data;
 
   private:
-	RingBuffer *buf;
+	SerialRingBuffer *buf;
 	uint32_t baudrate;
 	uint16_t config;
 

cores/common/arduino/libraries/api/SoftwareSerial/SoftwareSerial.h

@@ -27,7 +27,7 @@ typedef enum {
 
 typedef struct {
 	SoftState state;
-	RingBuffer *buf;
+	SerialRingBuffer *buf;
 	uint8_t byte;
 	pin_size_t pin;
 	void *param;

cores/common/base/lt_config.h

@@ -77,6 +77,10 @@
 #define LT_UART_DEFAULT_SERIAL LT_UART_DEFAULT_PORT
 #endif
 
+#ifndef LT_SERIAL_BUFFER_SIZE
+#define LT_SERIAL_BUFFER_SIZE 256
+#endif
+
 // Misc options
 #ifndef LT_USE_TIME
 #define LT_USE_TIME 0