Need support for `__lshrdi3`

[AngheloAlf]

GCC can emit a call for __lshrdi3 for a right shift between uint64_t when using -Os. GCC won't emit this call when using -Ofast, but it can still be good to have.

To recreate:

long long __ull_rshift(unsigned long long left, unsigned long long right) {
    return left >> right;
}