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

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@198073 91177308-0d34-0410-b5e6-96231b3b80d8