xhprof removed their composer.json file, adding it to our composer.json file so we can still use composer to manage xhprof. Added an extra script to make sure the update is clean for git users.
Skip xhprof building if phpize or make are missing.
Trimming output of build-xhprof.sh script.
Merge pull request #6107 from piwik/xhprof_composer

xhprof removed their composer.json file, adding it to our composer.json file so we can still use composer to manage xhprof. Includes output cleanup for build-xhprof.sh script.