Generate an APC prefix based on __FILE__

Relates to https://github.com/symfony/symfony-standard/issues/654
bug #3830 Generate an APC prefix based on __FILE__ (trsteel88)

This PR was submitted for the 2.4 branch but it was merged into the 2.3 branch instead (closes #3830).

Discussion
----------

Generate an APC prefix based on __FILE__

Relates to https://github.com/symfony/symfony-standard/issues/654

Commits
-------

55a7676 Generate an APC prefix based on __FILE__