Remove useless string copy. This fixes warnings on newer gccs with -Wformat-overflow:
dz80.c:440:20: warning: '-0' directive writing 2 bytes into a region of size between 0 and 79 [-Wformat-overflow=] dz80.c:437:20: warning: '+0' directive writing 2 bytes into a region of size between 0 and 79 [-Wformat-overflow=]
