Log Message:
Update php-debug to 2.5.5.

Wed, Jun 21, 2017 - xdebug 2.5.5

= Fixed bugs:

- Fixed issue #1439: TYPE_CHECK needs overloading due to smart branches
- Fixed issue #1444: Code Coverage misses a variable in a multi-line function
call
- Fixed issue #1446: Code Coverage misses elseif if it uses an isset with a
property