GCC 14 made passing an "incompatible" pointer type to another function an error.

• https://gcc.gnu.org/gcc-14/porting_to.html#c
• https://gcc.gnu.org/pipermail/gcc-cvs/2023-December/394351.html

The issue comes from builtin add-carry and sub-borrow.
Nim uint64 maps to NU64 which itself maps to uint64_t which itself maps to long unsigned int on x86-64.

However _addcarry_u64 has for signature unsigned char _addcarry_u64 (unsigned char c_in, unsigned __int64 a, unsigned __int64 b, unsigned __int64 * out)

unsigned __int64 maps to unsigned long long which is deemed incompatible with uint64_t so we need an explicit cast.