BlockDriver Internal32 changes
==============================
This driver now supports the first internal serial port of the
computer, plus all additional ports that are implemented as a
DeviceFS device.


2.00  27 Nov 2002  PRE
  - Internal32 created (from InternalPC) to run on 32-bit RISC OS.
  - Flag added to show 32-bit compliancy.

2.01  29 Nov 2002  PRE
  - Fixed problem that inhibited speeds > 19200 baud.
  - Removed self-modifying code.
  - Removed Archimedes hardware check.

2.02  29 Dec 2002  PRE
  - Added flag to show non-26-bit compliancy.
  - Fixed flushing of TX and RX buffers.

2.11  22 Apr 2004  PRE
  - Added basic support for 2nd serial port.
  - Numerous bug fixes.

2.12  27 Apr 2004  PRE
  - Extended to allow tracking of Driver and port number.

2.14  07 May 2004  PRE
  - Bugfix in Controllines for 1st serial port.

2.15  24 Jun 2004  PRE
  - Some optimisations.
  - Function codes 20 and 21 added to read RX/TX buffer handles.

2.16  26 Apr 2017  PRE
  - Various bugfixes.
  - Pre-initialisation added to allow port counting.
  - Dynamic port counting added, based on available serial devices
    in 'Devices:$'.
  - Default names of DeviceFS names for port 0 and port 1 corrected.
    Now uses 'Serial1' and 'Serial2' (was 'Serial' and 'Serial1').
  - Number of native serial ports now hardware-dependent (defaults to 2).
  - Neutral native port descriptions added.
  - Flag 19 added (ARM v7 compatible).
  - Support for more than 2 ports implemented.
  - First port still works via OS_SerialOp. All other ports via DeviceFS.

2.17  16 Feb 2019  PRE
  - Function 22: more reason codes added. Now returns DevFS name.

2.18  12 Jun 2020  PRE
  - Function 22 now also returns device description (USB).
  - Bugfix: Internal32,0 always reported RX activity.
  - Now accesses primary RISC OS serial port via DeviceFS rather than direct.
  - Separate block driver released for direct control of port 0 (SerialDirect).

2.19  09 Jul 2020  PRE
  - Bugfix: crashed when reading flowcontrol, due to 26-bit instruction.
  