[PATCH 0/6] MR1437: ntdll: Cleanup and refactor the x86_64 and i386 syscall dispatchers.

[Rémi Bernon (＠rbernon)]

In preparation for https://gitlab.winehq.org/wine/wine/-/merge_requests/1324.

This also begins preparation for a slightly different route than what the MR currently takes, with syscall flags eventually stored in the CounterTable rather than overusing syscall number unused bits.

To do that we're checking the syscall number and loading the syscall table (keeping it in %rbx/%ebx) earlier. This assumes that %rbx isn't modified in between, for instance by the eventual `SYS_arch_prctl` syscall, but I believe it is the case?