Use DoNotOptimize to prevent new/delete elision.

Use DoNotOptimize to prevent new/delete elision.

The new/delete tests, in particular those which test replacement
functions, often fail when the optimizer is enabled because the
calls to new/delete may be optimized away, regardless of their side-effects.

This patch converts the tests to use DoNotOptimize in order to prevent
the elision.

llvm-svn: 328245