[Oberon] Clean set of source files

[Peter De Wachter]

> I am trying to compile the compiler itself.
> Found that ORP.Mod.txt gives a TRAP 4 at pos 6262,
> when compiled with the compiler available in RISC.img.

Trap 4 is caused by dereferencing a NIL pointer. (Traps are listed in
section 12.7.10 .

If you're trying to build the entire compiler in a single command
("ORP.Compile ORS.Mod ORB.Mod ORG.Mod ORP.Mod ~"), this might be
caused by the system simply running out of memory. If no memory is
available, NEW returns a NIL pointer, which leads quickly to a trap 4.
This is easy to trigger with large compile jobs because the garbage
collector will not run until the command has completed.