fix @ptrFromInt to create a 0x0 address for ?*allowzero T instead of null

[Rexicon226]

closes #21775

[nektro]

why would that not be a compile error? allowzero and ? are mutually exclusive with regards to not increasing the size of the pointer, so having both shouldnt still be considered a pointer type. eg @sizeOf(?*allowzero T) will be 16 not 8 on 64bit platforms

[xdBronch]

same reason const n: ?u32 = @intCast(a); or anything else like that works

[nektro]

it does? 😳 TIL
I... definitely did not expect that