Merge branch '2.7' into 2.8

* 2.7:
  property constraints can be added in child classes
  added test for staticClassLoader in LazyLoadingMetadatafactory
  spelling fixes
  make sure that null can be the invalid value
  bumped Symfony version to 2.7.25
  updated VERSION for 2.7.24
  update CONTRIBUTORS for 2.7.24
  updated CHANGELOG for 2.7.24
  [FrameworkBundle] Simplify createPackageDefinition
  fix directory resource considers same timestamp not fresh
  return false early from directory resource

Author: nicolas-grekas

Compiler/ReplaceAliasByActualDefinitionPass.php

@@ -51,7 +51,7 @@ public function process(ContainerBuilder $container)
             if (isset($replacements[$targetId])) {
                 $container->setAlias($definitionId, $replacements[$targetId]);
             }
-            // No neeed to process the same target twice
+            // No need to process the same target twice
             if (isset($seenAliasTargets[$targetId])) {
                 continue;
             }