ir: Various fixes for comptime ptr handling

* Correctly fold ptrToInt on optional types
* Generate null as ConstPtrSpecialNull in intToPtr
* Correctly stop ptrToInt on ?*T where T is zero-sized

Closes #4535
55ea855e2cLemonBoy committed on 2/25/2020, 10:38:56 PM· committed by Andrew Kelleyparent8981221
3 files changedLine totals unavailable