add VerifyChecksum to HISTORY.md

Summary:
it's a new feature that'll be released in 5.8, introduced by PR #2498.
Closes https://github.com/facebook/rocksdb/pull/2759

Differential Revision: D5661923

Pulled By: ajkr

fbshipit-source-id: 9ba9f0d146c453715358ef2dd298aa7765649d7c

HISTORY.md

@@ -7,6 +7,7 @@
 * Replace dynamic_cast<> (except unit test) so people can choose to build with RTTI off. With make, release mode is by default built with -fno-rtti and debug mode is built without it. Users can override it by setting USE_RTTI=0 or 1.
 * Universal compactions including the bottom level can be executed in a dedicated thread pool. This alleviates head-of-line blocking in the compaction queue, which cause write stalling, particularly in multi-instance use cases. Users can enable this feature via `Env::SetBackgroundThreads(N, Env::Priority::BOTTOM)`, where `N > 0`.
 * Allow merge operator to be called even with a single merge operand during compactions, by appropriately overriding `MergeOperator::AllowSingleOperand`.
+* Add `DB::VerifyChecksum()`, which verifies the checksums in all SST files in a running DB.
 
 ### Bug Fixes
 * Fix wrong latencies in `rocksdb.db.get.micros`, `rocksdb.db.write.micros`, and `rocksdb.sst.read.micros`.