DebugInfo: Specify that a value is stored indirectly

This is a precursor to fix a regression caused by PR14763/r183329 where
the location of a non-trivial pass-by-value parameter ends up
incorrectly referring directly to the parameter (a pointer) rather than
the object pointed to by the pointer.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184365 91177308-0d34-0410-b5e6-96231b3b80d8