syz-extract was removing certain prefixes from syscall names, but this
caused some problems:
- freebsd* prefixes are for compatibility syscalls when the syscall ABI
has changed. For instance, we have both fstat() and
freebsd11_fstat(), and it is desirable to fuzz them both.
- Stripping prefixes may leave us with undefined SYS_ constants. This
resulted in some test failures in pkg/csource, which emitted code
referencing SYS_semctl when it should have been SYS___semctl.
Fix the problem by updating syscall descriptions to match the names
given by the FreeBSD kernel. Add some new descriptions for
compatibility syscalls, fix the mknodat() description (dev_t is now 64
bits wide on FreeBSD), and remove mknod$loop, which appears to be
Linux-specific.
This is mostly copied form linux.
We probably need better support for sharing descriptions
between multiple OSes. But there are lots of differences,
so this is not trivial.
