Upgrade to Symfony 2.7.6

I ran this update and there is a difference in the autoload_classmap.php file. I think it got missed because of a different location. Here is the missing change.

diff --git a/vendor/composer/autoload_classmap.php b/vendor/composer/autoload_classmap.php
index fac9eab..6d782e0 100644
--- a/vendor/composer/autoload_classmap.php
+++ b/vendor/composer/autoload_classmap.php
@@ -437,6 +437,7 @@
     'SebastianBergmann\\Environment\\Runtime' => $vendorDir . '/sebastian/environment/src/Runtime.php',
     'SebastianBergmann\\Exporter\\Exporter' => $vendorDir . '/sebastian/exporter/src/Exporter.php',
     'SebastianBergmann\\GlobalState\\Blacklist' => $vendorDir . '/sebastian/global-state/src/Blacklist.php',
+    'SebastianBergmann\\GlobalState\\CodeExporter' => $vendorDir . '/sebastian/global-state/src/CodeExporter.php',
     'SebastianBergmann\\GlobalState\\Exception' => $vendorDir . '/sebastian/global-state/src/Exception.php',
     'SebastianBergmann\\GlobalState\\Restorer' => $vendorDir . '/sebastian/global-state/src/Restorer.php',
     'SebastianBergmann\\GlobalState\\RuntimeException' => $vendorDir . '/sebastian/global-state/src/RuntimeException.php',

Also, I see there are security related fixes in the changelog. I am guessing this issue counts as critical but I will leave that for review.

#2608426: Upgrade to Symfony 2.7.6 is the exact same issue with some discussion about security.

Quoting from #2608426-3: Upgrade to Symfony 2.7.6:

bug #16108 [Security] #15764. Use SessionAuthenticationStrategy on RememberMe login
bug #16146 [Security] sync translations and add a test for it
bug #14842 [Security][bugfix] "Remember me" cookie cleared on logout with custom "secure"/"httponly" config options
bug #13627 [Security] InMemoryUserProvider now concerns whether user's password is changed when refreshing
bug #15895 [Security] Allow user providers to be defined in many files

And from comment 4 on the same issue:

All of those are part of the security component, which we don't use. They aren't security fixes itself.

Since there is already a patch here, should we mark that as duplicate, or post the patch to that issue?

Since there is already a patch here, should we mark that as duplicate, or post the patch to that issue?

Yeah let's mark the other issue as duplicate. Just wanted to point out the security aspect ...

Looks good to me. Needs to be triaged though.

I was going off the wrong tag description docs. Sorry.

Committed/pushed to 8.0.x, thanks!