Support switch statements in kernels

[1ntEgr8]

We should support switch statements in qcor kernels. We can definitely use if/else statements to express the same logic, but switch statements allow us to express equality-base conditional expressions more concisely.

enum Pauli {
  X,
  Y,
  Z
};

__qpu__ void test(qreg a, Pauli p) {
    switch (p) {
      case Pauli::X: qcor::X(a); break;
      case Pauli::Y: qcor::Y(a); break;
      case Pauli::Z: qcor::Z(a); break;
    }
}

int main() {
    qreg a = qalloc(2);
    test(a, Pauli::X); 
}