Apparently a boolean in php.ini is according to the documentation "on" or "off"…

Fixes itself.

This allows to check for specific values in the PHP.ini that ownCloud requires for full compatibility.

`mbstring.func_overload`: https://github.com/owncloud/core/issues/14372
`output_buffering`: http://doc.owncloud.org/server/8.0/admin_manual/configuration/big_file_upload_configuration.html#configuring-php

Fixes https://github.com/owncloud/core/issues/14372 and https://github.com/owncloud/core/issues/14412

on ownCloud upgrade: upgrade all apps in order, load important ones

Fix "other" app update stack

Fixes https://github.com/owncloud/core/issues/14356

This prevents a misusage of \OC\Files\View by calling it with user-supplied input. In such cases an exception is now thrown.

APCu before 4.0.6 is unbelievable buggy and tend to segfault the PHP process (i.e. the whole webserver)

This potentially fixes https://github.com/owncloud/core/issues/14175

Requires a backport to stable8

It still works otherwise, but without this, the performance optimization
of #13416 is defeated in these situations.

Fixes: #14048, #14104, calendar#712

This changeset removes the static class `OC_Request` and moves the functions either into `IRequest` which is accessible via `\OC::$server::->getRequest()` or into a separated `TrustedDomainHelper` class for some helper methods which should not be publicly exposed.

This changes only internal methods and nothing on the public API. Some public functions in `util.php` have been deprecated though in favour of the new non-static functions.

Unfortunately some part of this code uses things like `__DIR__` and thus is not completely unit-testable. Where tests where possible they ahve been added though.

Fixes https://github.com/owncloud/core/issues/13976 which was requested in https://github.com/owncloud/core/pull/13973#issuecomment-73492969

This change allows AppFramework applications to specify a custom CSP header for example when the default policy is too strict. Furthermore this allows us to partially migrate away from CSS and allowed eval() in our JavaScript components.

Legacy ownCloud components will still use the previous policy. Application developers can use this as following in their controllers:
```php
$response = new TemplateResponse('activity', 'list', []);
$cspHelper = new ContentSecurityPolicyHelper();
$cspHelper->addAllowedScriptDomain('www.owncloud.org');
$response->addHeader('Content-Security-Policy', $cspHelper->getPolicy());
return $response;
```

Fixes https://github.com/owncloud/core/issues/11857 which is a pre-requisite for https://github.com/owncloud/core/issues/13458 and https://github.com/owncloud/core/issues/11925

Some code paths called the `normalizePath` functionality with types other than a string which resulted in unexpected behaviour.

Thus the function is now manually casting the type to a string and I corrected the usage in list.php as well.

Otherwise logout can fail if the requesttoken contains a +

PHPStorm complained about those functions being declared as Internal. I doubt that this is actually the case since they are even in the public API.

* imageflip() isn't available in PHP < 5.5
* fixes #14130