[Vm-dev] [OpenSmalltalk/opensmalltalk-vm] Add accurate check for console stdio + add associated primitive (#254)

[akgrant43]

Hi Vincent,

This still isn't working because 
sqFileStdioHandlesIntoFile_WithHandle_IsWritable() doesn't take SQFile 
by reference (arrays are just pointers to the first element in C, which 
is why the array of SQFile structures doesn't need to be passed by 
reference explicitly):


```
sqFileStdioHandlesIntoFile_WithHandle_IsWritable(SQFile *file, HANDLE handle, int isWritable) {
        file->sessionID = thisSession;
        file->file = handle;
        file->writable = isWritable;
        file->lastOp = 0; /* unused on win32 */
        file->isStdioStream = isFileHandleATTY(handle);
        AddHandleToTable(win32Files, handle);
}


sqFileStdioHandlesInto(SQFile files[3])
{
        sqFileStdioHandlesIntoFile_WithHandle_IsWritable(&files[0], GetStdHandle(STD_INPUT_HANDLE), false);
        sqFileStdioHandlesIntoFile_WithHandle_IsWritable(&files[1], GetStdHandle(STD_OUTPUT_HANDLE), true);
        sqFileStdioHandlesIntoFile_WithHandle_IsWritable(&files[2], GetStdHandle(STD_ERROR_HANDLE), true);

        return 7;
}
```


I think that gets the basic changes you wanted done.  But it still 
leaves stdio in cygwin terminals broken.  After a bit more reading it 
looks like cygwin terminals and Windows ReadConsole() and WriteConsole() 
functions are fundamentally incompatible.

I don't understand what ReadConsole() and WriteConsole() provide in 
terms of benefits over FILE* streams, so I can't really comment on 
the cost of replacing them.

Eliot, what are your thoughts about moving the stdio functionlity to use 
FILE* streams instead of HANDLE streams?

I think that would allow the VM to use fread(), feof(), and fwrite() to 
read and write stdio to terminals (cygwin), consoles (windows), pipes 
and regular files.

Another option may be to leave the existing console functionality and 
use the connectToFileDescriptor() routine to separately open the stdio 
streams as FILE* streams.  The image can then decide how it wants to 
interact with stdio.

(we should probably move this conversation to vm-dev and out of this 
particular PR)


Thanks,
Alistair



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