Generate less dead code by deleting unreachable blocks at the end of functions (which would otherwise appear if a function ends with a return, for example).

// bug #191

int[3] a = [0: 0, 2: 42, 1: 1];

void main()
{
  assert(a[0] == 0);
  assert(a[1] == 1); // fails!
  assert(a[2] == 42);
}