Wrote empty definitions for some APIC functions

Started x86 interrupt setup code

src/x86/apic.c

@@ -0,0 +1,23 @@
+#include "apic.h"
+
+void apic_enable()
+{
+
+}
+
+void apic_eoi()
+{
+
+}
+
+void apic_send_ipi(
+    uint32_t vector,
+    enum apic_delivery_mode_t delivery_mode,
+    enum apic_destination_mode_t destination_mode,
+    enum apic_level_t level,
+    enum apic_trigger_mode_t trigger_mode,
+    enum apic_destination_shorthand_t shorthand,
+    uint32_t destination)
+{
+    
+}