[Request] Allow filtering 32 and 64 bits syscalls for x86-64.

[patlefort]

At the moment, it's not possible to filter both. If a filtered program call a 32 bits program, it will result in a bad system call. In libseccomp, one can differentiate between the 2 by checking for __X32_SYSCALL_BIT mask on the system call number. It would be very useful for my use case, filtering calls from a sandbox environment that may use 32 bits applications.

[colinmarc]

I would also use such a feature. I'm also a bit confused about the current API - does the filter just reject/kill syscalls with a different AUDIT_* arch? This could definitely be better documented.