minor symfony#16641 Tweaking deprecation message to include class name (weaverryan)

This PR was squashed before being merged into the 2.8 branch (closes symfony#16641).

Discussion
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Tweaking deprecation message to include class name

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

Before:

> Resource checking through ResourceInterface::isFresh() is deprecated since 2.8
> and will be removed in 3.0

After:

> The class Symfony\Bundle\AsseticBundle\Config\AsseticResource is performing
> resource checking through ResourceInterface::isFresh(), which is deprecated since 2.8
> and will be removed in 3.0

Commits
-------

07d627d Tweaking deprecation message to include class name

Author: fabpot

src/Symfony/Component/Config/Resource/BCResourceInterfaceChecker.php

@@ -29,7 +29,7 @@ public function supports(ResourceInterface $metadata)
 
     public function isFresh(ResourceInterface $resource, $timestamp)
     {
-        @trigger_error('Resource checking through ResourceInterface::isFresh() is deprecated since 2.8 and will be removed in 3.0', E_USER_DEPRECATED);
+        @trigger_error(sprintf('The class "%s" is performing resource checking through ResourceInterface::isFresh(), which is deprecated since 2.8 and will be removed in 3.0', get_class($resource)), E_USER_DEPRECATED);
 
         return parent::isFresh($resource, $timestamp); // For now, $metadata features the isFresh() method, so off we go (quack quack)
     }