For DW_TAG_template_type_parameter the actual passed in type could
be void and therefore not have a type entry. Only add the type if
it is non-void and provide a testcase.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187966 91177308-0d34-0410-b5e6-96231b3b80d8