[DebugInfo/PDB] Adding getUndecoratedNameEx and IPDB interfaces for IDiaEnumTables and IDiaTable.

Initial changes to support debugging PE/COFF files with LLDB on Windows through DIA SDK.
There is another set of changes required on the LLDB side before this does anything.

Differential Revision: https://reviews.llvm.org/D39517

llvm-svn: 318403