Various debug conditional compilation cleanup (#2915)

* Global: Define DEBUG as 0 if not already defined

* Clean up DEBUG-guarded code

src/d/d_msg_class.cpp

@@ -1971,7 +1971,7 @@ void jmessage_tSequenceProcessor::do_end() {
 
 bool jmessage_tSequenceProcessor::do_isReady() {
     jmessage_tReference* pReference = (jmessage_tReference*)getReference();
-    #ifdef DEBUG
+    #if DEBUG
     if (pReference->getRevoMessageID() != 0) {
         return 0;
     }