No longer leaking Argument objects after calling createArgument. However, since an OwningPtr cannot live in a std::vector yet, there are some manual deletions that have a FIXME attached to them. These will go away once C++11 support is allowed.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@197715 91177308-0d34-0410-b5e6-96231b3b80d8