tidy-up: miscellaneous

- tool_bname: scope an include.
- `endif` comments.
- Markdown fixes.
- comment tidy-ups.
- whitespace, newlines, indent.

Closes #20309

src/tool_cb_hdr.c

@@ -143,7 +143,7 @@ locdone:
     curlx_free(copyloc);
   }
 }
-#endif
+#endif /* LINK */
 
 /*
  * Copies a filename part and returns an ALLOCATED data buffer.