Merge branch '2.2' into 2.3

* 2.2:
  corrected English grammar (s/does not exists/does not exist)
  [Process] Add more precision to Process::stop timeout
  [Process] Avoid zombie process in case of unit tests failure
  [Process] Fix #8739
  [Process] Add failing test for #8739
  [Process] Fix CS
  Fixed documentation grammar for AuthenticationManagerInterface::authenticate()
  [Validator] fixed the wrong isAbstract() check against the class (fixed #8589)
  [TwigBridge] Prevent code extension to display warning
  Use strstr instead of strpos

Conflicts:
	src/Symfony/Component/Finder/Shell/Command.php
	src/Symfony/Component/Process/Process.php

.gitignore

@@ -1,4 +1,3 @@
 vendor/
 composer.lock
 phpunit.xml
-

ClassLoader.php

@@ -177,7 +177,7 @@ class ClassLoader
         $classPath .= str_replace('_', DIRECTORY_SEPARATOR, $className).'.php';
 
         foreach ($this->prefixes as $prefix => $dirs) {
-            if (0 === strpos($class, $prefix)) {
+            if ($class === strstr($class, $prefix)) {
                 foreach ($dirs as $dir) {
                     if (file_exists($dir.DIRECTORY_SEPARATOR.$classPath)) {
                         return $dir.DIRECTORY_SEPARATOR.$classPath;