as-8080, as-z80: change behavior of ORG

[vbmacher]

ORG pseudocode should not change physical location of the code, just it should set different address of current instruction.

Instead, there should be other psudo-instruction which does that (e.g. ORG_LOAD, LOAD, LORG, ...)

This feature should help writing self-relocating programs, like boot loaders.