#25 Fix CRC status, revert to default SPI lib

- Revert SPI to default lib by default. Configure via RF24_config.h #24
- Corrected CRC status reporting per https://github.com/evorios by
checking AA register

RF24.cpp

@@ -1292,9 +1292,11 @@ void RF24::setCRCLength(rf24_crclength_e length)
 rf24_crclength_e RF24::getCRCLength(void)
 {
   rf24_crclength_e result = RF24_CRC_DISABLED;
+  
   uint8_t config = read_register(CONFIG) & ( _BV(CRCO) | _BV(EN_CRC)) ;
+  uint8_t AA = read_register(EN_AA);
   
-  if ( config & _BV(EN_CRC ) )
+  if ( config & _BV(EN_CRC ) || AA)
   {
     if ( config & _BV(CRCO) )
       result = RF24_CRC_16;

RF24_config.h

@@ -24,7 +24,7 @@
   //#define FAILURE_HANDLING
   //#define SERIAL_DEBUG  
   //#define MINIMAL
-  #define SPI_UART
+  //#define SPI_UART
   //#define SOFTSPI
   /**********************/
   

RPi/RF24/RF24.cpp

@@ -1233,8 +1233,9 @@ rf24_crclength_e RF24::getCRCLength(void)
 {
   rf24_crclength_e result = RF24_CRC_DISABLED;
   uint8_t config = read_register(CONFIG) & ( _BV(CRCO) | _BV(EN_CRC)) ;
+  uint8_t AA = read_register(EN_AA);
   
-  if ( config & _BV(EN_CRC ) )
+  if ( config & _BV(EN_CRC ) || AA)
   {
     if ( config & _BV(CRCO) )
       result = RF24_CRC_16;