Update release version to 6.19 (#8083)

Summary:
Update release version to 6.19

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8083

Test Plan: no code change

Reviewed By: riversand963

Differential Revision: D27222083

Pulled By: zhichao-cao

fbshipit-source-id: 94b49997019347e6e6a9e341837f4f9d3149428c

HISTORY.md

@@ -1,5 +1,5 @@
 # Rocksdb Change Log
-## Unreleased
+## 6.19.0 (03/21/2021)
 ### Bug Fixes
 * Fixed the truncation error found in APIs/tools when dumping block-based SST files in a human-readable format. After fix, the block-based table can be fully dumped as a readable file.
 * When hitting a write slowdown condition, no write delay (previously 1 millisecond) is imposed until `delayed_write_rate` is actually exceeded, with an initial burst allowance of 1 millisecond worth of bytes. Also, beyond the initial burst allowance, `delayed_write_rate` is now more strictly enforced, especially with multiple column families.

include/rocksdb/version.h

@@ -10,7 +10,7 @@
 #include "rocksdb/rocksdb_namespace.h"
 
 #define ROCKSDB_MAJOR 6
-#define ROCKSDB_MINOR 18
+#define ROCKSDB_MINOR 19
 #define ROCKSDB_PATCH 0
 
 // Do not use these. We made the mistake of declaring macros starting with