Add the support of "ItaniumPartialDemangler" in libcxxabi

Hi, guys,

Some debug tool(i.e dbx) needs the runtime to provide the component names for the demangled name(i.e qualifier, base name etc). I notice that, the Demangler in llvm indeed provides the interface to retrieve this information. However, the demangler in the libcxxabi didn’t. I can fully understand that what we need to do is just to implement the __cxa_demangle() api that defined in ABI. I wonder if we could add some routines in the libcxxabi to retrieve the component names to make it more powerful, together with the full demangled name. Thank you.

Best regards

XLC++ Compiler Frontend Developer

IBM China Development Lab, Shanghai

“All things are difficult before they are easy.”