[sv-bc] Problem with $ferror in 1364 standard

The definition of $ferror in section 17.2.7 of the 1364 LRM is unclear,
and may be incorrect or incomplete.

The text refers to an error in "the most recent file I/O operation".
This appears to be wrong.  Like the C ferror() function, $ferror is
passed a file descriptor argument.  This implies that it returns the
most recent error *for that file descriptor*, like ferror() does.
If the intent was to return the error for the most recent file I/O
operation on any file, there would be no need for such an argument.
So the text should be clarified to say "the most recent file I/O
operation on the file descriptor fd".

However, this does not provide a way to find out the reason for an
error in $fopen.  If $fopen fails, it returns a null file descriptor.
Without a file descriptor, $ferror has no information about what
file you want the last error for.  In C, you cannot use ferror() to
find out the reason for a failure in fopen().  You have to check
errno instead.  Verilog does not provide this alternate mechanism.

Note that 17.2.1 talks about errors in $fopen, and then says that
"Applications can call $ferror to determine the cause of the most
recent error (see 17.2.7)."  This implies that $ferror can be used
to find out the cause of a failure in $fopen.

This leaves various possible interpretations:

1. The implication in 17.2.1 is incorrect, and you cannot use $ferror
   to find out the cause of a failure in $fopen.  Since there is no
   alternate mechanism for finding out the cause of the failure, this
   seems bad.

2. The syntax in 17.2.7 is incorrect, and there is no fd argument to
   $ferror.  $ferror always reports the status of the most recent file
   I/O operation on any file and there is no mechanism for finding out
   the status on a particular file descriptor.  This may not be bad
   as long as you always check status immediately after an error, though
   it does not match C as you would expect.

3. Like interpretation 2, but the syntax is correct and there is a
   completely useless fd argument to $ferror.  This would be stupid.

4. You can use $ferror on a file descriptor to get the most recent file
   I/O status on that file descriptor.  If you pass a null descriptor,
   it is assumed to have come from a failed $fopen, and the status of
   the last $fopen (or the last failed $fopen) is returned instead.