Debug Info: add a newly-created DIE to a parent in the same function.

With this commit, all DIEs created in CompileUnit will be added to parents
inside the same function. Also make getOrCreateTemplateType|Value functions
private.

No functionality change.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193002 91177308-0d34-0410-b5e6-96231b3b80d8