Document the Engine renaming better & link to relevant issues/PRs

include/Engine.h

@@ -42,6 +42,18 @@ class Song;
 class Ladspa2LMMS;
 
 
+// Note: This class is called 'LmmsCore' instead of 'Engine' because of naming
+// conflicts caused by ZynAddSubFX. See https://github.com/LMMS/lmms/issues/2269
+// and https://github.com/LMMS/lmms/pull/2118 for more details.
+//
+// The workaround was to rename Lmms' Engine so that it has a different symbol
+// name in the object files, but typedef it back to 'Engine' and keep it inside
+// inside of Engine.h so that the rest of the codebase can be oblivious to this
+// issue (and it could be fixed without changing every single file).
+
+class LmmsCore;
+typedef LmmsCore Engine;
+
 class EXPORT LmmsCore : public QObject
 {
 	Q_OBJECT
@@ -134,8 +146,5 @@ class EXPORT LmmsCore : public QObject
 };
 
 
-// define the class as "LmmsCore" to avoid symbol name clashes with ZynAddSubFx's Engine class,
-// but typedef to Engine so that the rest of Lmms can pretend the name clash doesn't exist.
-typedef LmmsCore Engine;
-
 #endif
+