Fix build; add RNG code

include/Actor/Actor.hpp

@@ -26,6 +26,8 @@ struct Actor_UnkStruct_012 {
     /* 14 */ u32 mUnk_14;
     /* 18 */ u32 mUnk_18;
     /* 1c */
+
+    Actor_UnkStruct_012();
 };
 
 struct Actor_UnkStruct_020 {

include/System/Random.hpp

@@ -0,0 +1,22 @@
+#pragma once
+
+#include "global.h"
+#include "types.h"
+
+struct Random {
+    /* 00 */ u64 mRandomValue;
+    /* 08 */ u64 mFactor;
+    /* 10 */ u64 mAddend;
+    /* 18 */
+
+    /**
+     * Generate a random number from 0 (inclusive) to `max` (exclusive)
+     */
+    inline u32 Next(u32 max) {
+        mRandomValue = mAddend + mFactor * mRandomValue;
+        u64 result   = (mRandomValue >> 32) * max;
+        return result >> 32;
+    }
+};
+
+extern Random *gRandom;