PR22877: When constructing an array via a constructor with a default argument

PR22877: When constructing an array via a constructor with a default argument
in list-initialization, run cleanups for the default argument after each
iteration of the initialization loop.

We previously only ran the destructor for any temporary once, at the end of the
complete loop, rather than once per iteration!

Re-commit of r302750, reverted in r302776.

llvm-svn: 302817