removed the deprecated TwigCoreExtension class
removed deprecated locale_fallback setting
removed the deprecated Compiler class and the doc on the phar
removed conditions about the request stack as Symfony 2.4+ is required now
removed obsolete comment
minor #847 [2.0] removed deprecated features (fabpot)

This PR was merged into the 2.0-experimental branch.

Discussion
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[2.0] removed deprecated features

Commits
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c2a2e51 removed obsolete comment
a8d8993 removed conditions about the request stack as Symfony 2.4+ is required now
8a6e0e4 removed the deprecated Compiler class and the doc on the phar
75a5aa8 removed deprecated locale_fallback setting
639502b removed the deprecated TwigCoreExtension class