REG_INC notes going AWOL during reload

[Herman ten Brugge]

I missed the test program in Michael Hayes bug report. I did sent it
to him so here it is:

char line[4] = { '1', '9', '9', '\0' };

int main()
{
  char *ptr = line + 3;

  while ((*--ptr += 1) > '9') *ptr = '0';
  if (line[0] != '2' || line[1] != '0' || line[2] != '0')
    abort();
  return 0;
}

I found problems on the c4x and m68k targets. The result on these targets
is '2::' instead of '200'. The store '0' insn is probably removed in flow
because of the missing REG_INC as Michael explained in this bug report.
Probably all targets with auto incr/decr have this problem. Perhaps this
small program could be added to the torture tests.

	Herman.