[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

if (!remaining) { // list-directed or NAMELIST: check for separators
       }
     }
     return std::nullopt;
   }
 
   // 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);
       } else if (!AdvanceRecord()) {
         return std::nullopt;
       }
       ch = GetCurrentChar();
     }

flang/runtime/namelist.cpp

 static inline char32_t GetComma(IoStatementState &io) {
   return io.mutableModes().editingFlags & decimalComma ? char32_t{';'}
                                                        : char32_t{','};
 }
 
 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()) &&
         io.Emit(&ch, 1);
   }};
   const auto EmitUpperCase{[&](const char *str) -> bool {
     if (connection.NeedAdvance(std::strlen(str)) &&
         !(io.AdvanceRecord() && io.Emit(" ", 1))) {
if (*ch == '/') {
       }
     }
   }
 }
 
 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);
   // Find this namelist group's header in the input
   io.BeginReadingRecord();
   std::optional<char32_t> next;
   char name[nameBufferSize];
   RUNTIME_CHECK(handler, group.groupName != nullptr);
if (!next || *next != '/') {
     return false;
   }
   io.HandleRelativePosition(1);
   return true;
 }
 
 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)) {
           do {
             io.HandleRelativePosition(1);
             ch = io.GetCurrentChar();
           } while (ch && IsLegalIdChar(*ch));
           ch = io.GetNextNonBlank();