System-call wrappers for glibc

I suspect that it's a side-effect that wiring up even completely architecture-independent system calls across all architectures used to be very complicated, so that system call additions tended to be spread across many kernel releases. With a multiplexer, you only have to go through the process once. Likewise for adding the system call wrapper to glibc.

Truly problematic are only system calls for which the intended implementation uses va_list in some way. The increased type safety may be worthwhile for separate functions, and it generally increases source portability once rarely used types change (e.g. file offsets with fcntl, times with futex). But that seems to be difficult to predict.