RFE: src/arch-syscall-check.c should also verify the presence of the __SNR_xxx defines

[pcmoore]

This came out of issue #314. While arch-syscall-check.c is good at ensuring the internal libseccomp syscall tables are consistent across arch/ABIs, it doesn't verify that we have the necessary __SNR_xxx definitions to match.

[pcmoore]

It's worth noting that the move to the CSV syscall table means the current tests in src/arch-syscall-check.c are largely pointless; the automatically generated syscall tables should always be in sync across the different arch/ABIs. This isn't to see we need to drop these existing checks, but if dropping these checks makes it easier to solve this issue I have no problem doing that.