Avoid overloading on 32 bit architectures

Avoid overloading on 32 bit architectures

Forwarded: no

unsigned and size_t are equivalent on 32 bit architectures,
so only define the size_t based overload of advance on 64
bit architectures.
https://wiki.debian.org/ArchitectureSpecificsMemo

Gbp-Pq: Name 32bit-avoid-overloading.patch