Factorization and consistency
- create a fpm_use_error_log() to check when file or stderr should be used
- use it everywhere for consistency
- add some comments
Merge branch 'PHP-5.6'

* PHP-5.6:
  Factorization and consistency - create a fpm_use_error_log() to check when file or stderr should be used - use it everywhere for consistency - add some comments