Added PT3 flow control functionality

[badbunny@tfsp.saic.com (Brendan Hoar)]

Hello world!

If you are using PT3, a hardware handshaking modem & cable a PT3 port driver
that supports hardware handshaking and a PT3 modem driver that ends with
(RTS/CTS), this may be useful to you.  Otherwise, skip this message.

What this does is create two small routines that PT3 can install in memory and
use to call its own port drivers in order to change the status of flow control.
The macros which call these use an undocumented command called 'OVERLAY'.  This
is also how PT3.CONVERT is implemented (check out PT3.GLOBAL to verify this).

Why would you ever need to change the status of flow control?  Well, if you
quit PT3 and then return to it later without dropping your connection, PT3 will
default to flow control off.  Previous to this, the only way to rectify the
situation was to hang up and redial.  The same thing happens if you used the
PT3 Installer while you are on-line.

As usual, many thanks to Greg Schaefer for providing me with this workaround.



*** REMEMBER TO CHANGE THE TEXT STRINGS TO MATCH THE CORRECT PATH!!!

---- Add the lines below to the start of your PT3.GLOBAL file ----
*
   Additions to PT3 Global Macros here
*

@@h
  OVerlay "/h1/pt3/enable.flow"
  NOte "If CTS was high, hardware flow control is now enabled."
ex

@@j
  OVerlay "/h1/pt3/disable.flow"
  NOte "Hardware flow control disabled."
ex
---- snip ----
Then take the lines below starting with MTR and put them in a separate text
file in your PT3 directory.  Then EXEC that text file from BASIC.

MTR
2000:a9 03 4c 05 08
bsave enable.flow,a$2000,l$10
2000:a9 04 4c 05 08
bsave disable.flow,a$2000,l$10
3d0g