Add missing SPCR definitions. (#243)

teensy3/avr_emulation.cpp

 #include "SPIFIFO.h"
 
 uint8_t SPCRemulation::pinout = 0;
+SPCRemulation SPCR;
 #if defined(KINETISL)
 uint8_t SPCR1emulation::pinout = 0;
+SPCR1emulation SPCR1;
 #endif
 #if defined(__MK64FX512__) || defined(__MK66FX1M0__)
 uint8_t SPCR1emulation::pinout = 0;
+SPCR1emulation SPCR1;
 uint8_t SPCR2emulation::pinout = 0;
+SPCR2emulation SPCR2;
 #endif
 #ifdef HAS_SPIFIFO