Merge branch '2.3' into 2.7

* 2.3:
  [Process] Enhance compatiblity with --enable-sigchild
  [Process] Always call proc_close
  [Validator] Updated Luxembourgish translations for 2.8
  [FrameworkBundle] prevent cache:clear creating too long paths

Conflicts:
	src/Symfony/Component/Process/Tests/ProcessTest.php
	src/Symfony/Component/Process/Tests/SigchildDisabledProcessTest.php
	src/Symfony/Component/Process/Tests/SigchildEnabledProcessTest.php
	src/Symfony/Component/Process/Tests/SimpleProcessTest.php
	src/Symfony/Component/Validator/Resources/translations/validators.lb.xlf

Author: nicolas-grekas

Command/CacheClearCommand.php

@@ -54,7 +54,9 @@ protected function configure()
     protected function execute(InputInterface $input, OutputInterface $output)
     {
         $realCacheDir = $this->getContainer()->getParameter('kernel.cache_dir');
-        $oldCacheDir = $realCacheDir.'_old';
+        // the old cache dir name must not be longer than the real one to avoid exceeding
+        // the maximum length of a directory or file path within it (esp. Windows MAX_PATH)
+        $oldCacheDir = substr($realCacheDir, 0, -1).('~' === substr($realCacheDir, -1) ? '+' : '~');
         $filesystem = $this->getContainer()->get('filesystem');
 
         if (!is_writable($realCacheDir)) {
@@ -75,7 +77,7 @@ protected function execute(InputInterface $input, OutputInterface $output)
             // the warmup cache dir name must have the same length than the real one
             // to avoid the many problems in serialized resources files
             $realCacheDir = realpath($realCacheDir);
-            $warmupDir = substr($realCacheDir, 0, -1).'_';
+            $warmupDir = substr($realCacheDir, 0, -1).('_' === substr($realCacheDir, -1) ? '-' : '_');
 
             if ($filesystem->exists($warmupDir)) {
                 if ($output->isVerbose()) {
@@ -114,8 +116,6 @@ protected function execute(InputInterface $input, OutputInterface $output)
      */
     protected function warmup($warmupDir, $realCacheDir, $enableOptionalWarmers = true)
     {
-        $this->getContainer()->get('filesystem')->remove($warmupDir);
-
         // create a temporary kernel
         $realKernel = $this->getContainer()->get('kernel');
         $realKernelClass = get_class($realKernel);