Set SPI_HAS_TRANSACTION to 1 and implement buffer transfer

See: https://github.com/arduino/Arduino/blob/master/hardware/arduino/avr/libraries/SPI/src/SPI.h#L21, https://www.arduino.cc/en/Reference/SPITransfer, and https://github.com/arduino/Arduino/blob/master/hardware/arduino/avr/libraries/SPI/src/SPI.h#L244-L257

Author: Lauszus

libraries/SPI/SPI.h

@@ -24,7 +24,7 @@
 #include <Arduino.h>
 #include <stdlib.h>
 
-#define SPI_HAS_TRANSACTION
+#define SPI_HAS_TRANSACTION 1
 
 // This defines are not representing the real Divider of the ESP8266
 // the Defines match to an AVR Arduino on 16MHz for better compatibility
@@ -63,6 +63,7 @@ class SPIClass {
   void beginTransaction(SPISettings settings);
   uint8_t transfer(uint8_t data);
   uint16_t transfer16(uint16_t data);
+  void transfer(void * data, uint32_t size) { transferBytes((uint8_t*)data, (uint8_t*)data, size); data -= size; };
   void write(uint8_t data);
   void write16(uint16_t data);
   void write16(uint16_t data, bool msb);