Tweaks to hash primitives

Summary: [Folly] Tweaks to hash primitives: twang, jenkins_rev, fnv

Reviewed By: ot, luciang

Differential Revision: D23290185

fbshipit-source-id: 080dfa8a5f357065473f3973654c91d01c683c3c

folly/compression/test/CompressionTest.cpp

@@ -82,7 +82,7 @@ ByteRange DataHolder::data(size_t size) const {
 }
 
 uint64_t hashIOBuf(const IOBuf* buf) {
-  uint64_t h = folly::hash::FNV_64_HASH_START;
+  uint64_t h = folly::hash::fnv64_hash_start;
   for (auto& range : *buf) {
     h = folly::hash::fnv64_buf(range.data(), range.size(), h);
   }