Added enum for timer interrupt vector

src/x86/interrupts.h

@@ -24,6 +24,7 @@ enum interrupt_code_t
     EXCEPTION_SIMD_FLOATING_POINT = 19,
     EXCEPTION_VIRTUALIZATION = 20,
     EXCEPTION_SECURITY = 30,
+    ISR_APIC_TIMER = 64,
     ISR_AP_START = 127,
     ISR_SYSCALL = 128
 };