Improve LLDB's embedded C++ demangler by addressing the following two issues:

1) Preserve ref qualification state in a local variable while parsing a nested name.  Previously, the state was recorded in the shared db reference and could therefore be overwritten when parsing multiple levels of nested names (e.g.: when a qualified name has qualified template args.)

2) Address an off-by-one error when testing whether or not a thunk is non-virtual.  This resulted in the demangled identifying all thunks as non-virtual.