merged branch lsmith77/forward_compat (PR #2526)
merged branch lsmith77/forward_compat (PR #2526)

Commits
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b6bf018 tweaked error handling for the forward compatibility
dd606b5 added note about the purpose of this class
c1426ba added locale handling forward compatibility
10eed30 added MessageDataCollector forward compatibility

Discussion
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Forward compat

Bug fix: no
Feature addition: yes
Backwards compatibility break: no
Symfony2 tests pass: yes
Fixes the following tickets: #2522

nichdu/HttpFoundation,mneuhaus/HttpFoundation,oswaldderiemaecker/HttpFoundation,ygerasimov/HttpFoundation,symfony/http-foundation,symfony/HttpFoundation