test PATCH method for update action in generated scaffold controller test rather than PUT

Refactor Routing::Mapper#matches?

Pass in `--local` when doing `gem install` for local gems. [ci skip]

Explain the possible IP precautions

Restore original remote_ip algorithm.

Proxy servers add X-Forwarded-For headers, resulting in a list of IPs. We
remove trusted IP values, and then take the last given value, assuming that
it is the most likely to be the correct, unfaked value. See [1] for a very
thorough discussion of why that is the best option we have at the moment.

[1]: http://blog.gingerlime.com/2012/rails-ip-spoofing-vulnerabilities-and-protection/

Fixes #7979

Remove another unnecessary dup

Conflicts:
	activerecord/lib/active_record/dynamic_matchers.rb

do not append a second slash when using `trailing_slash: true`

Fix a number of validation/style errors

 * <pre> is not allowed to be nested inside of <p> elements in HTML
 * Indentation of </p> doesn't match corresponding <p>
 * <p> element not explicitly closed
 * One more </div> than <div>

In each case, the template was fixed to match how a HTML5 parser would "see"
the resulting page.

Remove unnecessary #dup

Allow toggling dumps on error page

Replace #flatten with Array()

Cleanup the CSS on the new error page.

refactoring to_sym of Symbol in preload

Add source code left padding on error pages

This is version of #8640 for master

Add missing changelog entry for #8676 [ci skip]

remove meaningless AS::FrozenObjectError