Bury leaked pointers in a global array to silence a leak detector in --disable-free mode

Summary:
This is an alternative to http://llvm-reviews.chandlerc.com/D2475
suggested by Chandler.

Reviewers: chandlerc, rnk, dblaikie

CC: cfe-commits, earthdok

Differential Revision: http://llvm-reviews.chandlerc.com/D2478