Support for PCjr keyboard IR reciever option

Currently disabled as it Error B's

src/include/86box/m_pcjr.h

@@ -68,6 +68,7 @@ typedef struct pcjr_s {
     uint8_t    pb;
 
     uint8_t    option_fdc;
+    uint8_t    option_ir;
 
     pc_timer_t send_delay_timer;