Added PSR-4 ClassLoader to list
feature #3972 Added PSR-4 to Class Loaders list (dosten)

This PR was merged into the 2.5 branch.

Discussion
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Added PSR-4 to Class Loaders list

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | yes
| Applies to    | 2.5+
| Fixed tickets | none

Commits
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d1c95ce Added PSR-4 ClassLoader to list