[flang][runtime] Signal END from character input

[klausler]

Summary

There's code in EditCharacterInput() that causes that template function
to silently return false if it is invoked at the end of the input file.
This overrides other checks that properly call SignalEnd() later.

flang/runtime/descriptor-io.h

if (listOutput) {
       if (!ListDirectedCharacterOutput(io, *listOutput, x, length)) {
         return false;
       }
     } else if (auto edit{io.GetNextDataEdit()}) {
       if constexpr (DIR == Direction::Output) {
         if (!EditCharacterOutput(io, *edit, x, length)) {
           return false;
         }
-      } else {
+      } else { // input
         if (edit->descriptor != DataEdit::ListDirectedNullValue) {
           if (EditCharacterInput(io, *edit, x, length)) {
             anyInput = true;
           } else {
             return anyInput && edit->IsNamelist();
           }
         }
       }

flang/runtime/edit-input.cpp

case 'Z':
     return EditBOZInput<4>(io, edit, x, length * sizeof *x);
   default:
     io.GetIoErrorHandler().SignalError(IostatErrorInFormat,
         "Data edit descriptor '%c' may not be used with a CHARACTER data item",
         edit.descriptor);
     return false;
   }
   const ConnectionState &connection{io.GetConnectionState()};
-  if (connection.IsAtEOF()) {
-    return false;
-  }
   std::size_t remaining{length};
   if (edit.width && *edit.width > 0) {
     remaining = *edit.width;
   }
   // When the field is wider than the variable, we drop the leading
   // characters.  When the variable is wider than the field, there can be
   // trailing padding.
   const char *input{nullptr};