use proper PRId64 macros for TraceFrame printing
correct syscall number for x86-64 restart_syscall syscall
use inline assembly for sigreturn test
make exec_file_supported return true for x86-64 hosts
only check for user_fpxregs_struct on x86 hosts

There's no such structure on x86-64, so we get compilation errors.
fix static_assert for flock/flock64 size difference
flip on x86-64 bits in kernel_abi.h