Merge branch '6.4' into 7.0

* 6.4:
  Update UPGRADE-6.4.md
  Add native return types to fix compat with v7

Author: nicolas-grekas

CHANGELOG.md

@@ -10,6 +10,7 @@ CHANGELOG
 ---
 
  * Add FQCN and FQCN::method aliases for routes loaded from attributes/annotations when applicable
+ * Add native return type to `AnnotationClassLoader::setResolver()`
 
 6.2
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