Dos-handler

This is an OS4 port of the "DOS DEVICE DRIVER EXAMPLE FOR AZTEC C" by Matthew
Dillon (http://aminet.net/package.php?package=dev/src/DosDev.lha). OS4
modifications and port by Fredrik Wikstrom (fredrik at a500 dot org).

It's a handler/filesystem for a simple dynamic sized "RAM Disk:". There are a
few issues with it (listed below), but is probably still useful as example
source though..

Issues:
 - DSIs when more than one program tries to access the same file (?)
 - Multiview complains about "not enough data" when opening a text file
 - Icon->Information on the disk shows bad data
 - Volume name shows up correctly with "C:info" in the "volumes available" and
in ASL requster but not in shell prompt or icon->info. Shows up correctly in
Workbench after being renamed but not before

When compiled with -DDEBUG the handler prints out debug output (packets
received, etc.) using exec's DebugPrintF. SashimiPPC can be used to capture this
output.

Compiling the handler:

1. make

To enable debug output remove the '#' before -DDEBUG in the Makefile.

Mounting the device:

1. mount test: from mountlist

This mounts a disk with:
Device name: "TEST:"
Volume name: "TEST Disk:"

Changes:
0.5 (29-Nov-06)
 - renamed handler to dos-handler to avoid confusion, since it's a handler, not
a device
 - handler now compiled without debug output (it's much faster now)
0.4 (22-Jun-06)
 - modified code to make use of MakeDosEntry()/FreeDosEntry
 - added ACTION_RENAME_DISK support (not fully working for some reason)
0.3 (19-Jun-06)
 - added version string
 - added support for ACTION_FH_FROM_LOCK packet
0.2 (16-Jun-06)
 - added support for ACTION_EXAMINE_FH packet
 - fixed handling of ACTION_PARENT packet
0.1 (15-Jun-06)
 - first released version