Merge branch 'hotfix/yaml-dev-version'

Fixes for symfony/yaml autoloading
Reworked polyfill support for Zend\Stdlib\ArrayObject

- Instead of using an autoload file, instead created two separate classes, named
  after the type of support they provide. The file Zend\Stdlib\ArrayObject now
  simply has a conditional in it; based on the condition met, a class_alias() is
  created -- and from then on, that alias will be used for
  Zend\Stdlib\ArrayObject.

- Removed autoload.files entries from composer.json files; no longer necessary.

- One test failure currently in doing a comparison of merged array objects; will
  investigate in a later commit.
Reworked polyfill support for Zend\Session

- Created Zend\Session\Container and Zend\Session\Storage\SessionArrayStorage
  namespaces. Each contains PhpLegacyCompatibility and PhpReferenceCompatibility
  classes. The classes with the same name as the new namespaces each use
  conditionals to execute class_alias() commands in order to perform
  version-specific polyfills.
- Removed compatibility/autoload.php from composer.json autoload.files; no
  longer necessary.
- All tests are running!
Solved failing test in ArrayObject tests

- changed a typehint from "ArrayObject" to "self"
Fix failing Zend\Session test under 5.3.3

- bad import
Re-added autoload.php files

- BC measure, so that code referencing these files doesn't break
Fix typo

- per @DASPRiD
Fix polyfill support issue in CSRF validator

- typehint on AbstractContainer
- when instantiating a Container instance, use fully qualified class name in
  order to trigger alias
Typehint on AbstractContainer, but instantiate Container

- Imports will work against class_alias
- Typehinting works, *except* when using mocks, as mocks do not take
  into account class aliasing.
Renamed compat autoload files and marked as deprecated

- moved autoload.php files into compatibility subdirs where they belong
- marked each with @deprecated annotation
Remove class_exists check

- bad cut-and-paste
Fake scanners out

- Use __halt_compiler(), and then define stub class, in order to trick
  classmap compilers into thinking a class exists.
Class stubs to force classmap generation
Allow finding class definitions following halt_compiler

- Allows finding class definitions following halt_compiler directives,
  effectively allowing polyfill support in classmap generation.
Added note in README about new polyfill support
Updated README to detail full change for polyfills
Trigger E_USER_DEPRECATED in deprecated polyfill autoload files
Simpler polyfill support

- Have a base class that extends a polyfill class
  - makes classmap generation simpler
  - makes typehinting and mock objects simpler
Revert changes to ClassFileLocator

- No longer necessary to do the halt_compiler hack
Revert changes to CSRF validator

- No longer necessary