01: Fixup & extend vm_regs example

Firstly, calculating flags register is done properly (this time
flags are cleared too, not just set). Secondly, general purpose
registers are extended for new C and D registers. And finally,
instruction set is extended among with example which now
implements a basic for(i = 0; i < 10; i++) () loop.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>