database: DBPlaneShortName() return const char *

database/DBtechname.c

@@ -347,11 +347,11 @@ DBTypeShortName(
     return ("???");
 }
 
-char *
-DBPlaneShortName(pNum)
-    int pNum;
+const char *
+DBPlaneShortName(
+    int pNum)
 {
-    NameList *tbl;
+    const NameList *tbl;
 
     for (tbl = dbPlaneNameLists.sn_next;
 	    tbl != &dbPlaneNameLists;

database/database.h.in

@@ -1062,7 +1062,7 @@ extern HashTable	DBTypeAliasTable;
 extern char		*DBPlaneLongNameTbl[NP];
 
     /* Gives a short name for each plane: */
-extern char		*DBPlaneShortName();
+extern const char	*DBPlaneShortName();
 
     /* Gives for each plane a mask of all tile types stored in that plane: */
 extern TileTypeBitMask	DBPlaneTypes[NP];