__cxa_demangle: Fix constructor cv qualifier handling

[tberghammer]

Summary

Previously if we parsed a constructor then we set parsed_ctor_dtor_cv
to true and never reseted it. This causes issue when a template argument
references a constructor (e.g. type of lambda defined inside a
constructor) as we will have the parsed_ctor_dtor_cv flag set what will
cause issues when parsing later arguments.

[compnerd]

Can you please ensure that you cross-port this into llvm/lib/Demangle/ItaniumDemangle.cpp?

libcxxabi/trunk/src/cxa_demangle.cpp

 {
     if (first != last)
     {
         save_value<decltype(db.encoding_depth)> su(db.encoding_depth);
         ++db.encoding_depth;
         save_value<decltype(db.tag_templates)> sb(db.tag_templates);
         if (db.encoding_depth > 1)
             db.tag_templates = true;
+        save_value<decltype(db.parsed_ctor_dtor_cv)> sp(db.parsed_ctor_dtor_cv);
+        db.parsed_ctor_dtor_cv = false;
         switch (*first)
         {
         case 'G':
         case 'T':
             first = parse_special_name(first, last, db);
             break;
         default:
           {

libcxxabi/trunk/test/test_demangle.pass.cpp

//    {"_Z1fM1XRFivEMS_OFivEMS_KOFivE", "f(int (X::*)() &, int (X::*)() &&, int (X::*)() const &&)"},
     {"_ZN5test71XIiEC1IdEEPT_PNS_5int_cIXplL_ZNS_4metaIiE5valueEEsrNS6_IS3_EE5valueEE4typeE", "test7::X<int>::X<double>(double*, test7::int_c<(test7::meta<int>::value) + (test7::meta<double>::value)>::type*)"},
     {"_ZN5test81fIiEEvNS_5int_cIXsrNS_4metaIT_E4typeE5valueEEE", "void test8::f<int>(test8::int_c<test8::meta<int>::type::value>)"},
     {"_ZN5test91fIiNS_1XEEENS_9supermetaIT_E5applyIT0_E4typeEv", "test9::supermeta<int>::apply<test9::X>::type test9::f<int, test9::X>()"},
     {"_ZN6test101fIidEENS_1XIT_E10definitionIT0_EES2_S5_", "test10::X<int>::definition<double> test10::f<int, double>(int, double)"},
     {"_ZZ2f5vE1a", "f5()::a"},
     {"_ZZ2f6vE1b", "f6()::b"},
     {"_ZNV3$_35test9Ev", "$_3::test9() volatile"},
     {"_ZN5Test8I3$_2EC1ES0_", "Test8<$_2>::Test8($_2)"},
+    {"_Z3fooIZN3BarC1EvE3$_0EvT_", "void foo<Bar::Bar()::$_0>(Bar::Bar()::$_0)"},
     {"_ZGVZN1N1gEvE1a", "guard variable for N::g()::a"},
     {"_ZplRK1YRA100_P1X", "operator+(Y const&, X* (&) [100])"},
     {"_Z1fno", "f(__int128, unsigned __int128)"},
     {"_Z1fM1SKFvvE", "f(void (S::*)() const)"},
     {"_Z3ft7IiEN11__enable_ifIXsr16__is_scalar_typeIT_EE7__valueEvE6__typeEv", "__enable_if<__is_scalar_type<int>::__value, void>::__type ft7<int>()"},
     {"_Z3ft7IPvEN11__enable_ifIXsr16__is_scalar_typeIT_EE7__valueEvE6__typeEv", "__enable_if<__is_scalar_type<void*>::__value, void>::__type ft7<void*>()"},
     {"_ZN6PR57968__fill_aIiEENS_11__enable_ifIXntsrNS_11__is_scalarIT_EE7__valueEvE6__typeEv", "PR5796::__enable_if<!(PR5796::__is_scalar<int>::__value), void>::__type PR5796::__fill_a<int>()"},
     {"_ZN11Expressions2f1ILi1EEEvPAplngT_Li2E_i", "void Expressions::f1<1>(int (*) [(-(1)) + (2)])"},