[Simh] fprint_sym and parse_sym limitation

[Paul Koning]

> On Sep 23, 2015, at 11:39 AM, Mark Pizzolato - Info Comm <Mark at infocomm.com> wrote:
> 
> On Wednesday, September 23, 2015 at 8:31 AM, Paul Koning wrote:
>> ...
>> I'm going to make a stab at updating simh.doc with what I can see, and
>> description of what I understand or TBS for what I see but don't know how to
>> document.
> 
> Great!
> 
> Please start from the latest simh.doc from the github repo.  

Done.  I sent a pull request.  This is my first, so if I'm doing this wrong, please give me directions on how to do it right.

> 
> Please come back with your TBS list and we'll flesh out what is needed.

There are three: in DEVICE, the "description" field; in UNIT, the "iostarttime" field; and for REG_UNIT the way in which the address of the data is computed.

By the way, the existence of REG_UNIT contradicts the statement earlier in the doc that only devices have registers...

	paul