[flang] Correct implementation of WAIT with no ID

[klausler]

Summary

Previous one was returning a bogus error status about a bad WAIT
statement ID number.

flang/runtime/io-api.cpp

if (ExternalFileUnit * unit{ExternalFileUnit::LookUp(unitNumber)}) {
     if (id != 0) {
       io.GetIoErrorHandler().SetPendingError(IostatBadWaitUnit);
     }
     return &io;
   }
 }
 Cookie IONAME(BeginWaitAll)(
     ExternalUnit unitNumber, const char *sourceFile, int sourceLine) {
-  return IONAME(BeginWait)(unitNumber, 0 /*no ID=*/);
+  return IONAME(BeginWait)(unitNumber, 0 /*no ID=*/, sourceFile, sourceLine);
 }
 
 Cookie IONAME(BeginClose)(
     ExternalUnit unitNumber, const char *sourceFile, int sourceLine) {
   if (ExternalFileUnit * unit{ExternalFileUnit::LookUpForClose(unitNumber)}) {
     return &unit->BeginIoStatement<CloseStatementState>(
         *unit, sourceFile, sourceLine);
   } else {

flang/runtime/unit.h

 
 class ExternalFileUnit : public ConnectionState,
                          public OpenFile,
                          public FileFrame<ExternalFileUnit> {
 public:
   explicit ExternalFileUnit(int unitNumber) : unitNumber_{unitNumber} {
     isUTF8 = executionEnvironment.defaultUTF8;
     asyncIdAvailable_.set();
+    asyncIdAvailable_.reset(0);
   }
   ~ExternalFileUnit() {}
 
   int unitNumber() const { return unitNumber_; }
   bool swapEndianness() const { return swapEndianness_; }
   bool createdForInternalChildIo() const { return createdForInternalChildIo_; }
 
   static ExternalFileUnit *LookUp(int unit);

flang/runtime/unit.cpp

if (!mayAsynchronous()) {
     return static_cast<int>(*least);
   } else {
     handler.SignalError(IostatTooManyAsyncOps);
     return -1;
   }
 }
 
 bool ExternalFileUnit::Wait(int id) {
-  if (id < 0 || asyncIdAvailable_.test(id)) {
+  if (static_cast<std::size_t>(id) >= asyncIdAvailable_.size() ||
+      asyncIdAvailable_.test(id)) {
     return false;
   } else {
-    if (id == 0) {
+    if (id == 0) { // means "all IDs"
       asyncIdAvailable_.set();
+      asyncIdAvailable_.reset(0);
     } else {
       asyncIdAvailable_.set(id);
     }
     return true;
   }
 }
 
 void ChildIo::EndIoStatement() {