Many changes to reduce complaints from CppCheck. Several latent bugs fixes, but probably some new typos introduced

tools/mksyscall.c

@@ -606,7 +606,7 @@ int main(int argc, char **argv, char **envp)
             fprintf(stderr, "Missing option argument, option: %c\n", optopt);
             show_usage(argv[0]);
 
-           break;
+          default:
             fprintf(stderr, "Unexpected option: %c\n", ch);
             show_usage(argv[0]);
         }