Generate an APC prefix based on __FILE__

Closes #654
feature #657 Generate an APC prefix based on __FILE__ (trsteel88)

This PR was merged into the 2.6-dev branch.

Discussion
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Generate an APC prefix based on __FILE__

Closes #654

Commits
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3be1eee Generate an APC prefix based on __FILE__
added back a comment that aas removed in the previous merge
make config_dev.yml a valid YML file

`%..%` must be wrapped by quotes, or YML file is not valid!
bug #687 make config_dev.yml a valid YML file (jdespatis)

This PR was submitted for the master branch but it was merged into the 2.5 branch instead (closes #687).

Discussion
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make config_dev.yml a valid YML file

`%..%` must be wrapped by quotes, or YML file is not valid!

Commits
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848b095 make config_dev.yml a valid YML file
Merge branch '2.5'

* 2.5:
  make config_dev.yml a valid YML file
Merge branch 'symfony-standard/master'