[rfc] Replacing FNV and hash32 with Paul Hsieh's SuperFastHash

Hi, I've recently noticed that hash table use in nullfs was inefficient, 1/3 to half of buckets remained unused. I've started investigating it further and came across SuperFastHash hashing function, SFH (SuperFastHash) has BSD license, used in WebKit and other open source projects. Detailed

Re: [dtrace] syscall provider naming convention.

I have one comment though.  I am not sure about renaming syscall.ko to syscall_freebsd.ko. You mean systrace_freebsd.ko. I've renamed it for consistency with other systrace provider variants. I can change it back. Perhaps we could keep the old name?  Or add a new module under that name that