Go through the really awkward dance required to delete the memory
allocated by setupterm. Without this, some folks are seeing leaked
memory whenever this routine is called more than once. Thanks to Craig
Topper for the report.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188615 91177308-0d34-0410-b5e6-96231b3b80d8