gh-111178: fix clang-cl compilation of Modules/mmapmodule.c

[chris-eibl]

After #129784 clang-cl fails with a compilation error for mmap__sizeof__method in Modules/mmapmodule.c:

..\Modules\mmapmodule.c(1201,25): error : incompatible function pointer types initializing 'PyCFunction' (aka 'struct _object *(*)(struct _object *, struct _object *)') with an expression of type 'PyObject *(PyObject *, void *)' (aka 's
truct _object *(struct _object *, void *)') [-Wincompatible-function-pointer-types] [e:\cpython_clang\PCbuild\pythoncore.vcxproj]

I think this is a skip-news.

• Issue: UBSan: Calling a function through pointer to incorrect function type is undefined behavior #111178

[picnixz]

@vstinner

I'd like to merge this one with title:

gh-111178: fix clang-cl compilation of `Modules/mmapmodule.c` post gh-129784 (#130446)

and commit body:

The `PyCFunction` cast on `mmap__sizeof__method` was removed but the method was not updated accordingly.

[vstinner]

LGTM

[picnixz]

Thanks for the fix. I needed to fix some UBSan issues without any IDE or compiler support so it wasn't always easy :')