[PDB] Rename some files in the native reader.

By calling these NativeType<foo>.cpp, they will all be sorted
together, and it also distinguishes the types from the symbols.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@341609 91177308-0d34-0410-b5e6-96231b3b80d8
11 files changed