Two Windows-only compile errors blocked the mingw cross-compile:
* `<winsock2.h>` transitively includes `<rpc.h>`, which defines
`#define interface struct`. The file uses `interface` as a loop
variable name in three for-loops, so on mingw it expanded into
`for(... struct : ...)` and cascaded into a wall of unrelated parse
errors. Undefine the macro right after the Windows headers in the
global module fragment.
* `static_cast<uint16_t>` in the port-probe helper failed because
mingw's `<stdint.h>` typedefs are in the global module fragment and
the C-namespace `::uint16_t` isn't anchored into the module purview
on this toolchain. `import std;` does export `std::uint16_t`, so
qualify the cast.
Verified by running `crafter-build --target=x86_64-w64-mingw32` end to
end and the full test suite (13 passed, 5 environment-skipped).
