Various debug conditional compilation cleanup (#2915)

* Global: Define DEBUG as 0 if not already defined

* Clean up DEBUG-guarded code

src/d/d_meter_HIO.cpp

@@ -801,7 +801,7 @@ void dMeter_drawLightDropHIO_c::genMessage(JORMContext* mctx) {
 #endif
 
 dMeter_drawHIO_c::dMeter_drawHIO_c() {
-    #ifdef DEBUG
+    #if DEBUG
     field_0x8_debug = 0;
     #endif
     mLifeTopPosX = 40.0f;