tidy-up: Markdown, clang-format nits

- drop leading indent from Markdown.
- switch to Markdown section markers where missing.
- move `&&` and `||` to the end of the line (C, Perl).
- openssl: add parenthesis to an if sub-expression.
- misc clang-format nits.
- unfold Markdown links.
- SSL-PROBLEMS.md: drop stray half code-fence.

Closes #20402

lib/doh.h

@@ -23,8 +23,8 @@
  * SPDX-License-Identifier: curl
  *
  ***************************************************************************/
-
 #include "urldata.h"
+
 #ifdef USE_HTTPSRR
 # include <stdint.h>
 #endif