Allow custom asset host to be passed in asset_url
Improve documentation for asset_url

Updated CHANGELOG.md with entry about :host in asset_url
Fixed duplicate subscribers in ActiveSupport::Subscriber

ActiveSupport::Subscriber no longer creates multiple subscribers when
you redefine a method.
Add controller and action name to the instrumentation payload
Add multiple lines message support for SSE module
Use block parameter rather than `$1` during `gsub!` so `ActiveSupport::SafeBuffer` values aren't mangled.

Fixes #15064
Require active_support/core_ext/string/output_safety and use html_safe rather than use non-public SafeBuffer API.
Update and add tests in array_ext_test.rb

- Fix `test_to_with_instruct` typo to `test_to_xml_with_instruct`

- Rename `test_to_xml` to `test_to_xml_with_hash_elements` to make test
name more specific.

- Add `test_to_xml_with_non_hash_elements` and
`test_to_xml_with_non_hash_different_type_elements`

  `to_xml` behaves different when containing elements are same and
  different types.

- Add `test_to_xml_with_indent_set`
Update require in `array_ext_test.rb`

Removed `FIMXE` tag to require necessary file but not the whole core_ext
simplify AC:ViewPaths::_prefixes. by making it recursively traversing up the inheritance chain, classes can override local prefixes.
deprecate AbC:Base::parent_prefixes.
rename ::_local_prefixes to ::local_prefixes to state the public attribute.
document the latter.
make ::local_prefixes private, test overriding it and remove documentation for overriding ::_parent_prefixes.
Do not check defined?(CGI) on every call #to_query
Fix how to compute class name on habtm namespaced.

Thank's for @laurocaetano for the help with tests. :smiley:

Fixes #14709
Merge pull request #15091 from printercu/patch-5

Do not check defined?(CGI) on every call #to_query
[postgres] include PgArrayParser directly and only load/include ArrayParser if not found
Use i18n master to run tests
options already have symbolized keys, so we can avoid this call
the :only_path option is applied by the time the helper is called
just merge instead of dup and merge
use fewer method calls to determine the url_for options