Updated php55 segfault fix

@glennpratt and @bjaspan

* pulled in latest facebook/xhprof commits
* updated the segfault fix to use the code from https://github.com/facebook/xhprof/pull/33 instead of pull 32
* added a pull request to kovalenko/xhprof with these updates - the changes seem to be stalled on this dev signing a CLA... https://github.com/kovalenko/xhprof/pull/1