Fixing wrong link in 'Ruby on Rails Security Guide' [ci skip]

The URL

http://www.h-online.com/security/Symantec-reports-first-active-attack-on-a-DSL-router--/news/102352

points to an article titled 'The H is closing down'. The good one is:

http://www.h-online.com/security/news/item/Symantec-reports-first-active-attack-on-a-DSL-router-735883.html
Rename the primary key index when renaming a table in pg

Backport of dcc143cd702bfbfef9cb92e1fde75171d088a5ac

Fixes #12856
Closes #14088
Correct example in the engines testing guide [ci skip]

Reference #17453

Conflicts:
	guides/source/engines.md
Add array support when time zone aware attributes are enabled

Conflicts:
	activerecord/test/cases/adapters/postgresql/array_test.rb
Remove some warnings
Remove more warnings
Includes HABTM returns correct size now. It's caused by the join dependency
only instantiates one HABTM object because the join table hasn't a primary key.
Updated commit from @bigxiang commit dbaa837

Fixes #16032.

Examples:

    before:

    Project.first.salaried_developers.size # => 3
    Project.includes(:salaried_developers).first.salaried_developers.size # => 1

    after:

    Project.first.salaried_developers.size # => 3
    Project.includes(:salaried_developers).first.salaried_developers.size # => 3
fix preload habtm associations with hashed conditions, fixes #15244