Merge branch '2.3' into 2.7

* 2.3:
  [travis] timeout the sigchild tests at 60s
  CS: Single line comments should use double slashes (//) and not hash (#).
  Do not use HttpKernel Extension when not needed
  bumped Symfony version to 2.3.37
  updated VERSION for 2.3.36
  update CONTRIBUTORS for 2.3.36
  updated CHANGELOG for 2.3.36
  use nowdoc instead of heredoc

Conflicts:
	src/Symfony/Bundle/FrameworkBundle/Command/ConfigDumpReferenceCommand.php
	src/Symfony/Bundle/FrameworkBundle/Command/RouterApacheDumperCommand.php
	src/Symfony/Bundle/FrameworkBundle/Command/RouterMatchCommand.php
	src/Symfony/Bundle/FrameworkBundle/Translation/Translator.php
	src/Symfony/Bundle/TwigBundle/Command/LintCommand.php
	src/Symfony/Component/Config/Tests/Definition/Dumper/YamlReferenceDumperTest.php
	src/Symfony/Component/Debug/ExceptionHandler.php
	src/Symfony/Component/HttpKernel/Kernel.php
	src/Symfony/Component/Routing/Generator/Dumper/PhpGeneratorDumper.php

Tests/ConstraintViolationListTest.php

@@ -110,7 +110,7 @@ public function testToString()
             $this->getViolation('Error 5', '', '[baz]'),
         ));
 
-        $expected = <<<EOF
+        $expected = <<<'EOF'
 Root:
     Error 1
 Root.foo.bar:

Tests/ConstraintViolationTest.php

@@ -26,7 +26,7 @@ public function testToStringHandlesArrays()
             null
         );
 
-        $expected = <<<EOF
+        $expected = <<<'EOF'
 Root.property.path:
     Array
 EOF;
@@ -45,7 +45,7 @@ public function testToStringHandlesArrayRoots()
             null
         );
 
-        $expected = <<<EOF
+        $expected = <<<'EOF'
 Array.some_value:
     42 cannot be used here
 EOF;