made browser logs commented by defaults (refs #8413)
merged branch symfony/monolog-tweaks (PR #569)

This PR was merged into the master branch.

Discussion
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made browser logs commented by defaults (refs symfony/symfony#8413)

FirePHP and ChromePHP are now disabled by default as they can make the application broke if the web server is not configured with large header sizes.

see symfony/symfony#8413

Commits
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262af2d made browser logs commented by defaults (refs #8413)
added an UPGRADE file for 2.4