Format code blocks inside markdown files (documentation)

There are issues with code blocks inside some *.md files (some files use code blocks syntax, some do not). First of all, it's not consistent but what's really bad is when *.md file is being displayed incorrectly. You can find an example of what I'm saying in CodingStandards.md under How we log changes section. ​https://github.com/torproject/tor/blob/master/doc/HACKING/CodingStandards.md#how-we-log-changes

Part of the git log output is still displayed as a regular text rather than a formatted code block.

Goal of this ticket is to go through all *.md files under doc and doc/HACKING directories and format code snippets accordingly.

```c
// code snippet
// written in
// C language

// command to be run
// inside bash

This should fix the issues described above and enable syntax highlighting on supported websites and editors.