Rename XHPAST build script
Summary: Historically XHPAST was built using a shell script, but it is now executed by PHP. We should eventually rename this file for consistency. To retain compatibility, we could possibly symlink build_xhpast.sh to build_xhpast.php and then check the value of $argv and emit a deprecation warning if build_xhpast.sh was called.
Test Plan: N/A
Reviewers: Blessed Reviewers, epriestley
Reviewed By: Blessed Reviewers, epriestley
Subscribers: Korvin, epriestley
Differential Revision: https://secure.phabricator.com/D12889