release 4.9 update version and history

Summary: update version and history

Test Plan: N/A

Reviewers: yiwu, sdong, IslamAbdelRahman, andrewkr

Reviewed By: andrewkr

Subscribers: andrewkr, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D59421

HISTORY.md

@@ -1,13 +1,16 @@
-# Unreleased
-### Public API Change
-* Deprecate BlockBaseTableOptions.hash_index_allow_collision=false
-* Deprecate options builder (GetOptions()).
-
 # Rocksdb Change Log
 ## Unreleased
+
+## 4.9.0 (6/9/2016)
 ### Public API changes
 * Add bottommost_compression option, This option can be used to set a specific compression algorithm for the bottommost level (Last level containing files in the DB).
 * Introduce CompactionJobInfo::compression, This field state the compression algorithm used to generate the output files of the compaction.
+* Deprecate BlockBaseTableOptions.hash_index_allow_collision=false
+* Deprecate BlockBaseTableOptions.hash_index_allow_collision=false
+* Deprecate options builder (GetOptions()).
+
+### New Features
+* Introduce NewSimCache() in rocksdb/utilities/sim_cache.h. This function creates a block cache that is able to give simulation results (mainly hit rate) of simulating block behavior with a configurable cache size.
 
 ## 4.8.0 (5/2/2016)
 ### Public API Change

include/rocksdb/version.h

@@ -5,7 +5,7 @@
 #pragma once
 
 #define ROCKSDB_MAJOR 4
-#define ROCKSDB_MINOR 8
+#define ROCKSDB_MINOR 9
 #define ROCKSDB_PATCH 0
 
 // Do not use these. We made the mistake of declaring macros starting with