Preboot scripts, redux.

The old implementation suffered from a couple problems:

• Chain booting and separate boot blocks made installation fussy
• I discovered that some OF versions don't quite claim more than a certain amount of memory for loading, making dual boot blocks waste a lot of precious RAM (I had two useless 4K stacks, for example). The symptom is a DSI during the actual load by the firmware - the same problem as seen trying to boot *BSD boot floppies on the 3400c. There might be a work around manually claiming the memory, but... heh.

I then realized I could have well added the preboot script at the end of the iquik.b block, and have the later be smart enough to eval the script prior to looking for the boot-file.

Usage is pretty simple (the -p option):

$ cat > hello.of 
$ cr cr cr ." Hello OF!!!" cr cr cr
$ iquik -p hello.of

Of course, this works only if booting iQUIK via partition zero (i.e. :0 or %BOOT). Presumably if you're running the ELF directly (hi CHRP!), you'll use a normal CHRP boot script.