Always use memory management wrappers

Use mem_*() wrappers instead of directly accessing libc functions when
allocating/deallocating memory.

Signed-off-by: Lukas Fleischer <lfleischer@calcurse.org>

src/io.c

@@ -821,8 +821,8 @@ void io_reload_data(void)
 				wins_launch_external(arg_todo);
 			}
 
-			xfree(path_apts_backup);
-			xfree(path_todo_backup);
+			mem_free(path_apts_backup);
+			mem_free(path_todo_backup);
 
 			/*
 			 * We do not directly write to the data files here;