[flang] Set right "inNamelist" flag

[klausler]

Summary

NAMELIST I/O was inconsistent in its choice of which set of I/O modes
to set the "inNamelist" flag. The wrong choice was in the set of modes
that are part of the persistent state of an I/O connection; the right
place is the set of modes that are reinitialized at the beginning of
each I/O statement so that they can be modified by READ/WRITE control
list specifiers and FORMAT control edit descriptors. Fix.

flang/runtime/io-stmt.h

   // Skips spaces, advances records, and ignores NAMELIST comments
   std::optional<char32_t> GetNextNonBlank() {
     auto ch{GetCurrentChar()};
-    bool inNamelist{GetConnectionState().modes.inNamelist};
+    bool inNamelist{mutableModes().inNamelist};
     while (!ch || *ch == ' ' || *ch == '\t' || (inNamelist && *ch == '!')) {
       if (ch && (*ch == ' ' || *ch == '\t')) {
         HandleRelativePosition(1);

flang/runtime/namelist.cpp

 bool IONAME(OutputNamelist)(Cookie cookie, const NamelistGroup &group) {
   IoStatementState &io{*cookie};
   io.CheckFormattedStmtType<Direction::Output>("OutputNamelist");
-  ConnectionState &connection{io.GetConnectionState()};
-  connection.modes.inNamelist = true;
+  io.mutableModes().inNamelist = true;
   char comma{static_cast<char>(GetComma(io))};
+  ConnectionState &connection{io.GetConnectionState()};
   // Internal functions to advance records and convert case
   const auto EmitWithAdvance{[&](char ch) -> bool {
     return (!connection.NeedAdvance(1) || io.AdvanceRecord()) &&

 bool IONAME(InputNamelist)(Cookie cookie, const NamelistGroup &group) {
   IoStatementState &io{*cookie};
   io.CheckFormattedStmtType<Direction::Input>("InputNamelist");
-  ConnectionState &connection{io.GetConnectionState()};
-  connection.modes.inNamelist = true;
+  io.mutableModes().inNamelist = true;
   IoErrorHandler &handler{io.GetIoErrorHandler()};
   auto *listInput{io.get_if<ListDirectedStatementState<Direction::Input>>()};
   RUNTIME_CHECK(handler, listInput != nullptr);

 
 bool IsNamelistName(IoStatementState &io) {
   if (io.get_if<ListDirectedStatementState<Direction::Input>>()) {
-    ConnectionState &connection{io.GetConnectionState()};
-    if (connection.modes.inNamelist) {
+    if (io.mutableModes().inNamelist) {
       SavedPosition savedPosition{io};
       if (auto ch{io.GetNextNonBlank()}) {
         if (IsLegalIdStart(*ch)) {