Qint integer division

[dakk]

Implement integer division // (known as floor_div) for Qint type using the following algorithm: Integer_division_(unsigned)_with_remainder

Handle division by constant using the same optimization method used for multiplying with constant implemented in #36

Tasks:

• [ ] Define a floor_div abstract method for Qtype
• [ ] Implement floor_div on Qint
• [ ] Make ast2logic handle ast.FloorDiv
• [ ] Write test cases in test_int.py
• [ ] Implement div by constant optimization (follow what I do in #36)

Please read CONTRIBUTING.md before contributing.

[ShayanMajumder]

Hi @dakk can you please review my latest merge request for this issue?