Possible php 7.1 modifications needed in civi core
Used https://github.com/Alexia/php7mar to scan the master(5.15.alpha1) version of civi code.
The issues found by the checker are listed in the attached file.
2018-12-22_15.32.20_all-civicrm.md
Maybe, it would be better to update the code based on the same?