minor #10644 Add upgrade instructions for the LoggerInterface that changed in Symfony 2.2 (ch3ric)

This PR was submitted for the 2.2 branch but it was merged into the 2.3 branch instead (closes #10644).

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Add upgrade instructions for the LoggerInterface that changed in Symfony 2.2

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6daa295 Add upgrade instructions for the LoggerInterface

UPGRADE-2.2.md

@@ -646,3 +646,23 @@
    extended with an optional `$context` array. This was necessary to allow for
    more complex use-cases that require context information during the
    (de)normalization and en-/decoding steps.
+
+### HttpKernel
+
+ * The `Symfony\Component\HttpKernel\Log\LoggerInterface` now extends `Psr\Log\LoggerInterface`.
+   So if you have implemented your own logger, you need to implement these methods:
+
+     * `emergency`
+     * `critical`
+     * `error`
+     * `warning`
+     * `log`
+
+#### Deprecations:
+
+ * The following Logger methods are deprecated and will be removed in 3.0. You should use the new PSR-3 methods:
+
+     * `emerg()` -> `emergency()`
+     * `crit()`  -> `critical()`
+     * `err()`   -> `error()`
+     * `warn()`  -> `warning()`