rework Registers to use more C++-y features for initialization
make Registers::total_registers() multi-architecture aware
teach preload.c to cope with differently-named syscalls for 32/64-bit
fix printf -Wformat error in preload.c
write traced syscall assembly for x86-64
make vsyscall hooking in libpreload x86-only
write cpuid_loop.S assembly for x86-64
un-#ifdef write_socketcall_args in task.cc