Squashed clang fixes

Summary:
  o workaround busybox bug 4123 by Doug Gilmore
  o fix xptr to y hack by Abdoulaye Walsimou Gaye
  o Fix string format security issue

Test Plan: verify

Reviewers: randall.rushing, synergy

Reviewed By: synergy

Differential Revision: http://review.codefirex.com/D621