simplify the hash API, call the hash function naturally

[rurban]

Call the hash function naturally
e.g. 32bit: uint32_t hash(const char* key, int len, uint32_t seed);
or 64bit: uint64_t hash(const char* key, int len, uint64_t seed);

Add pfhash templates for 32bit, 64bit (skip 128bit? not really needed).
Add \_test functions only for those with a different signature: e.g. seed as first PMurHash32(MH_UINT32 seed, const void *key, int len);

So one doesn't have to provide unnatural API's just to get an smhasher advantage.

Maybe provide hash classes for all functions, seperated into bitsize, seedsize, with optional init (clhash), and converter (seed first, ...)