llvm-undname: Yet more coverage for error paths
- For error returns in demangleSpecialTableNode(),
demangleLocalStaticGuard(), RTTITypeDescriptor,
demangleRttiBaseClassDescriptorNode(), demangleUnsigned(),
demangleUntypedVariable() (via RttiBaseClassArray)
- For ?_A and ?_P which are handled at early levels of the
demangler but are not implemented in a later stage; this
is now more obvious
- Replace a "default:" with an explicit list of cases, to
get -Wswitch check we list all cases
llvm-svn: 362520