Rewrote memory access handling to properly split execute from read, bus from CPU (but the mappings will still match until otherwise specified), and fixed exec[] usage by the mem_*_phys() functions.

src/cpu/x86seg.c

@@ -81,6 +81,8 @@ seg_reset(x86seg *s)
     s->limit_low = 0;
     s->limit_high = 0xffff;
     if (s == &cpu_state.seg_cs) {
+	if (!cpu_inited)
+		fatal("seg_reset(&cpu_state.seg.cs) without an initialized CPU\n");
 	s->base = AT ? (cpu_16bitbus ? 0x00ff0000 : 0xffff0000) : 0x000ffff0;
 	s->seg = AT ? 0xf000 : 0xffff;
     } else {