Fix a few compiler warnings

Source/diablo.cpp

@@ -1168,15 +1168,17 @@ static void PressChar(WPARAM vkey)
 			AutomapZoomOut();
 		}
 		return;
-	case 'v':
-		char *difficulties[3];
+	case 'v': {
 		char pszStr[120];
-		difficulties[0] = "Normal";
-		difficulties[1] = "Nightmare";
-		difficulties[2] = "Hell";
+		const char *difficulties[3] = {
+			"Normal",
+			"Nightmare",
+			"Hell",
+		};
 		sprintf(pszStr, "%s, mode = %s", gszProductName, difficulties[gnDifficulty]);
 		NetSendCmdString(1 << myplr, pszStr);
 		return;
+	}
 	case 'V':
 		NetSendCmdString(1 << myplr, gszVersionNumber);
 		return;

Source/objdat.cpp

@@ -8,7 +8,7 @@
 DEVILUTION_BEGIN_NAMESPACE
 
 /** Maps from dun_object_id to object_id. */
-int ObjTypeConv[] = {
+const int ObjTypeConv[] = {
 	0,
 	OBJ_LEVER,
 	OBJ_CRUX1,
@@ -151,7 +151,7 @@ int ObjTypeConv[] = {
 };
 
 /** Contains the data related to each object ID. */
-ObjDataStruct AllObjects[] = {
+const ObjDataStruct AllObjects[] = {
 	// clang-format off
 	// oload, ofindex,   ominlvl, omaxlvl, olvltype,        otheme,                  oquest,     oAnimFlag, oAnimDelay, oAnimLen, oAnimWidth, oSolidFlag, oMissFlag, oLightFlag, oBreak, oSelFlag, oTrapFlag
 	{      1, OFILE_L1BRAZ,    1,       4, DTYPE_CATHEDRAL, THEME_NONE,              -1,                 1,          1,       26,         64, TRUE,       TRUE,      FALSE,           0,        0, FALSE     },
@@ -317,7 +317,7 @@ const char *const ObjMasterLoadList[] = {
 	"LzStand"
 };
 /** Maps from object_graphic_id to object CEL name (Hellfire Crypt overwrite). */
-char *ObjCryptLoadList[] = {
+const char *ObjCryptLoadList[] = {
 	"L1Braz",
 	"L5Door",
 	"L5Lever",
@@ -376,7 +376,7 @@ char *ObjCryptLoadList[] = {
 	"LzStand",
 };
 /** Maps from object_graphic_id to object CEL name (Hellfire Hive overwrite). */
-char *ObjHiveLoadList[] = {
+const char *ObjHiveLoadList[] = {
 	"L1Braz",
 	"L1Doors",
 	"Lever",

Source/objdat.h

@@ -12,11 +12,11 @@ DEVILUTION_BEGIN_NAMESPACE
 extern "C" {
 #endif
 
-extern int ObjTypeConv[];
-extern ObjDataStruct AllObjects[];
+extern const int ObjTypeConv[];
+extern const ObjDataStruct AllObjects[];
 extern const char *const ObjMasterLoadList[];
-extern char *ObjCryptLoadList[];
-extern char *ObjHiveLoadList[];
+extern const char *ObjCryptLoadList[];
+extern const char *ObjHiveLoadList[];
 
 #ifdef __cplusplus
 }