tidy-up: miscellaneous

- INSTALL-CMAKE.md: add missing periods, text fixes.
- md4, md5: sync variables names.
- curl_trc: sync an argument type.
- docs/examples: sync debug/trace function copies, constify, tidy-ups.
- replace commented code with `#if 0`.
- drop redundant parenthesis (macro values, `return`, around single
  variables, function calls).
- fix indentation, apply clang-format in places.

Closes #20481

docs/examples/smooth-gtk-thread.c

@@ -152,7 +152,9 @@ static void *create_thread(void *progress_bar)
   gtk_widget_destroy(progress_bar);
 
   /* [Un]Comment this out to kill the program rather than pushing close. */
-  /* gtk_main_quit(); */
+#if 0
+  gtk_main_quit();
+#endif
 
   return NULL;
 }