platform: redeclared prototype for arch-specific signal mechanism

src/include/platform/platform.h

@@ -62,4 +62,4 @@ int platformConfigureIRQ(Thread *, int, IRQHandler *);  // configure an IRQ pin
 IRQCommand *platformGetIRQCommand();    // per-CPU IRQ command structure
 void platformIdle();            // to be called when the CPU is idle
 void platformCleanThread(void *, uintptr_t);   // garbage collector after thread is killed or replaced by exec()
-int platformSendSignal(Thread *, Thread *, int);
+int platformSendSignal(Thread *, Thread *, int, uintptr_t);