Add local and global arrays and array subscript operators.

[bit-hack]

The following should be legal:

int x[16];
int main() {
  int y[16];
  int z;
  z = 0;
  while (z < 16) {
    x[z] = z;
    y[z] = x[z];
    z = z + 1;
  }
  return y[4];
}

[bit-hack]

Both local and global arrays as well as the subscript operator are now supported.