support nested array of objects

[Vipul-Cariappa]

TODO: Needs tests.

cppyy.cppdef(r"""
constexpr int S = 4;

struct Klass {
    static int i;
    int k;
    Klass() : k(++i) {}
};
int Klass::i = 0;
Klass klasses[S][S + 3][S + 7];

bool consume_klass(Klass* c, int i, int j, int k) {
    if (c->k == ((S + 7) * (i * (S + 3) + j) + (k + 1))) return true;
    return false;
}
""")

assert gbl.klasses
for i in range(gbl.S):
  for j in range(gbl.S + 3):
    for k in range(gbl.S + 7):
      assert gbl.consume_klass(gbl.klasses[i][j][k], i, j, k)