Add array_has function
Fix a bug which caused irregular plural words to have an S appended when passed to Pluralizer::plural
Bugfix for long random strings and more randomness
Remove % from filenameFallback in Response::download

Because it's not allowed in the fallback name.
(See https://github.com/symfony/symfony/blob/v2.5.5/src/Symfony/Component/HttpFoundation/ResponseHeaderBag.php#L264-L277)
Fix a Str::snake Function
Improved The Str::snake Function #6100
Updated to be able to access all bags.

For ability to have a generic error handler for all bags in case they are grouped like `register[email]`. It's not possible to know what the grouping is unless `$errors->register->getMessages()` is specifically called.
Corrected Function Comment
Allows array_only to handle dotted keys
useless previous instanciation of $dotted variable
Ensure we can fetch an array with non existing keys
Merge branch '4.2'
Merge pull request #5746 from lucasmichot/4.2-array-only-dotted

[4.2] Allows Arr::only To Handle Dotted Keys
Merge branch '4.2'
Merge pull request #5765 from lucasmichot/4.2-support-helpers-array-has

[4.2] Added Arr::has
Merge branch '4.2'
Fix casing.
Fix casing and conflicts.
Merge pull request #6075 from egeriis/4.2

[4.2] Fixed A Pluralization Bug
Merge branch '4.2'