fix issue where $_ENV contains array vals

There are cases where $env or $_ENV can contain a value that is an array
This will cause Process to throw an Array to String conversion exception
Initially I submitted a patch of Process.php, however Fabien indicated
that it shouldn't be fixed there (see below pull request).

Before recently, a simple work around would be in php.ini to set:

  register_argc_argv = On

However with recent changes, this seems to no longer work.

Original pull request: https://github.com/symfony/symfony/pull/7354

See ticket https://github.com/symfony/symfony/issues/7196
[Process] moved env check to the Process class (refs #8227)
Merge branch '2.2' into 2.3

* 2.2:
  Throw exception if value is passed to VALUE_NONE input, long syntax
  fixed date type format pattern regex
  [FrameworkBundle] tweaked previous merge (refs #8242)
  do not re-register commands each time a Console\Application is run
  [Process] moved env check to the Process class (refs #8227)
  fix issue where $_ENV contains array vals
  [DomCrawler] Fix handling file:// without a host
  [Form] corrected interface bind() method defined against in deprecation notice
  [Finder] Fix SplFileInfo::getContents isn't working with ssh2 protocol

Conflicts:
	src/Symfony/Component/Console/Tests/Input/ArgvInputTest.php
	src/Symfony/Component/DomCrawler/Link.php
	src/Symfony/Component/Form/Form.php