DEHACKED lumps from IWAD now have precedence over embedded lumps and separate files

See https://forum.drdteam.org/viewtopic.php?t=7588

Processing order is now the same as in Chocolate Doom
prBoom+ loads separate files after all WAD lumps though
This makes sense but would change loading sequence existed in ZDoom for years

src/d_dehacked.cpp

@@ -2422,16 +2422,29 @@ static bool isDehFile(int lumpnum)
 		&& (0 == stricmp(extension, ".deh") || 0 == stricmp(extension, ".bex"));
 }
 
-int D_LoadDehLumps()
+int D_LoadDehLumps(DehLumpSource source)
 {
 	int lastlump = 0, lumpnum, count = 0;
 
 	while ((lumpnum = Wads.FindLump("DEHACKED", &lastlump)) >= 0)
 	{
+		const int filenum = Wads.GetLumpFile(lumpnum);
+		
+		if (FromIWAD == source && filenum > FWadCollection::IWAD_FILENUM)
+		{
+			// No more DEHACKED lumps in IWAD
+			break;
+		}
+		else if (FromPWADs == source && filenum <= FWadCollection::IWAD_FILENUM)
+		{
+			// Skip DEHACKED lumps from IWAD
+			continue;
+		}
+
 		count += D_LoadDehLump(lumpnum);
 	}
 
-	if (0 == PatchSize && dehload > 0)
+	if (FromPWADs == source && 0 == PatchSize && dehload > 0)
 	{
 		// No DEH/BEX patch is loaded yet, try to find lump(s) with specific extensions
 

src/d_dehacked.h

@@ -34,7 +34,13 @@
 #ifndef __D_DEHACK_H__
 #define __D_DEHACK_H__
 
-int D_LoadDehLumps();
+enum DehLumpSource
+{
+	FromIWAD,
+	FromPWADs
+};
+
+int D_LoadDehLumps(DehLumpSource source);
 bool D_LoadDehLump(int lumpnum);
 bool D_LoadDehFile(const char *filename);
 void FinishDehPatch ();

src/d_main.cpp

@@ -2507,6 +2507,9 @@ void D_DoomMain (void)
 		if (!batchrun) Printf ("DecalLibrary: Load decals.\n");
 		DecalLibrary.ReadAllDecals ();
 
+		// Load embedded Dehacked patches
+		D_LoadDehLumps(FromIWAD);
+
 		// [RH] Add any .deh and .bex files on the command line.
 		// If there are none, try adding any in the config file.
 		// Note that the command line overrides defaults from the config.
@@ -2528,7 +2531,7 @@ void D_DoomMain (void)
 		}
 
 		// Load embedded Dehacked patches
-		D_LoadDehLumps();
+		D_LoadDehLumps(FromPWADs);
 
 		// Create replacements for dehacked pickups
 		FinishDehPatch();