Dont' call screensaver when it is disabled.
Slightly simplify the program flow of main.
Remove mem.s from the build.

* This is unneeded, we can ignore the BASIc when started with run""
directly. Instead we can size the heap using progend and the AMSDOS ROM
bottom.
Remove now useless files

* mem.s is unneeded,
* labels are generated using a sed script.
Initialize BSS and disk ROM in CRT0.

* The BSS is needed for things to work (duh)
* The disk ROM must be initialized before allocating the heap.
Workaround SDCC bug.

SDCC would fail to initialize the first element of the process list.
Swap some conditions so the compiler can figure it out. Sigh.
Remove dependency on mem.s.
Remname CFS driver to AMSDOS.

Kernal? On CPC?