fmix32

MurmurHash3 finaliser mix invented by Austin Appleby - see for instance (the variant with uint32_t): https://chromium.googlesource.com/external/smhasher/%2B/58dd8869da8c95f5c26ec70a6cdd243a7647c8fc/MurmurHash3.cpp the code as such is public domain and is not licensed differently in this project