Fix: memory leak due to assigning result of strdup to a std::string

(cherry picked from commit 296194ad36)

src/newgrf.cpp

@@ -7563,7 +7563,7 @@ static void GRFInhibit(ByteReader *buf)
 		if (file != nullptr && file != _cur.grfconfig) {
 			grfmsg(2, "GRFInhibit: Deactivating file '%s'", file->GetDisplayPath());
 			GRFError *error = DisableGrf(STR_NEWGRF_ERROR_FORCEFULLY_DISABLED, file);
-			error->data = stredup(_cur.grfconfig->GetName());
+			error->data = _cur.grfconfig->GetName();
 		}
 	}
 }

src/signs_cmd.cpp

@@ -54,7 +54,7 @@ CommandCost CmdPlaceSign(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32
 		si->y = y;
 		si->z = GetSlopePixelZ(x, y);
 		if (!StrEmpty(text)) {
-			si->name = stredup(text);
+			si->name = text;
 		}
 		si->UpdateVirtCoord();
 		InvalidateWindowData(WC_SIGN_LIST, 0, 0);

src/town_cmd.cpp

@@ -2228,7 +2228,7 @@ CommandCost CmdFoundTown(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32
 		old_generating_world.Restore();
 
 		if (t != nullptr && !StrEmpty(text)) {
-			t->name = stredup(text);
+			t->name = text;
 			t->UpdateVirtCoord();
 		}