Merge pull request #421 from Lauszus/spi_has_transaction

Added missing SPI_HAS_TRANSACTION define, so libraries can tell that …

Author: Wenn0101

libraries/SPI/src/SPI.h

@@ -10,6 +10,10 @@
 
 #include "drivers/SPI.h"
 
+// SPI_HAS_TRANSACTION means SPI has beginTransaction(), endTransaction(),
+// usingInterrupt(), and SPISetting(clock, bitOrder, dataMode)
+#define SPI_HAS_TRANSACTION 1
+
 namespace arduino {
 
 class MbedSPI : public SPIClass