Fix cpuid on windows 64bits so that the x86 backend is enabled as expected

Fix cpuid on windows 64bits so that the x86 backend is enabled as expected

unsigned long isn't 64bits on win64, so the cpuid assembly code fails to
build during configure (%ebx and %rbx gets mixed in the assembly),
and the entire x86 backend gets disabled.

Use hwloc_uint64_t instead. It needs hwloc/autogen/config.h which isn't
ready during configure yet, so manually add #include/#define during
the cpuid check.

Thanks to Robin Scher for reporting the problem.