Add full I/O options for embedded files

[skx]

We embed the contents of static/A within our binary, such that binaries are always present at run-time.

(e.g. "A:!CCP", or "A:!DEBUG").

This is useful because it ensures that users don't need to hunt down binaries, and things are always present.

However it isn't possible to import arbitrary files - you cannot build a version of cpmulator by just adding "static/A/ZORK1.COM" and "static/A/ZORK1.DAT" because I only implemented a couple of the I/O options which are required for the CCP to load & execute them.

Add missing primitives for static files:

• BdosSysCallDeleteFile
  • Mark a file as deleted I guess? Or error out.
  • Do something anyway!
• BdosSysCallWrite
  • Fail? Pretend the files are immutable?
  • As per DeleteFile I guess
• BdosSysCallRenameFile
  • Fail? Pretend we're immutable?
  • As per above
• BdosSysCallFileSize
  • Implement this, properly.
• BdosSysCallReadRand
  • Implement this, properly.
• BdosSysCallWriteRand
  • Fail? Pretend we're immutable?
  • As per other failures.

Looks like I just need to add:

• [x] BdosSysCallFileSize
• [x] BdosSysCallReadRand

Of these adding only the last one would let us embed zork1 - which calls a lot of ReadRand against the associated data-file ZORK1.DAT:

A>!debug 1
031 RESERVE1
009 C_WRITESTRING
debug mode is on.
000 P_TERMCPM
032 F_USERNUM
013 DRV_ALLRESET
014 DRV_SET
..
A:>G:
G:>ZORK1
026 F_DMAOFF
025 DRV_GET
015 F_OPEN
026 F_DMAOFF
020 F_READ
026 F_DMAOFF
020 F_READ
..
033 F_READRAND
033 F_READRAND
033 F_READRAND
ZORK I: The Great Underground Empire
Copyright (c) 1981, 1982, 1983 Infocom, Inc. All rights
reserved.
ZORK is a registered trademark of Infocom, Inc.
Revision 88 / Serial number 840726

033 F_READRAND
033 F_READRAND
033 F_READRAND
033 F_READRAND
033 F_READRAND
033 F_READRAND
033 F_READRAND
033 F_READRAND
West of House
You are standing in an open field west of a white house, with
a boarded front door.
033 F_READRAND