syscount: Use ausyscalls if available to get syscall list
syscount: Use ausyscalls if available to get syscall list

If ausyscall is installed, it can provide a clean, up-to-date list of
syscall numbers for the current architecture. This is much more useful
than the default hardcoded list for x86-64, which is currently used by
syscount.

Try to run `ausyscall --dump` and parse the output before resorting to
the static list. Tested on FC/Linux 4.9 and produces 327 syscalls.

Resolves #1001.

tuxology/bcc,romain-intel/bcc,shodoco/bcc,iovisor/bcc,iovisor/bcc,iovisor/bcc,romain-intel/bcc,romain-intel/bcc,mcaleavya/bcc,shodoco/bcc,iovisor/bcc,brendangregg/bcc,mcaleavya/bcc,brendangregg/bcc,mcaleavya/bcc,brendangregg/bcc,shodoco/bcc,brendangregg/bcc,mcaleavya/bcc,shodoco/bcc,brendangregg/bcc,tuxology/bcc,mcaleavya/bcc,romain-intel/bcc,romain-intel/bcc,shodoco/bcc,tuxology/bcc,iovisor/bcc,tuxology/bcc,tuxology/bcc