convert CAZ, UndefValue, and CPN to use DenseMap's again, this time without

convert CAZ, UndefValue, and CPN to use DenseMap's again, this time without
using OwningPtr.  OwningPtr would barf when the densemap had to reallocate,
which doesn't appear to happen on the regression test suite, but obviously
happens in real life :)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@148700 91177308-0d34-0410-b5e6-96231b3b80d8