Update current version to 4.6

Summary: 4.5 is already cut, we can now increase the version in 4.6.

Test Plan: Not needed.

Reviewers: anthony, kradhakrishnan, andrewkr, yhchiang, IslamAbdelRahman

Reviewed By: IslamAbdelRahman

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D54963

include/rocksdb/version.h

@@ -5,7 +5,7 @@
 #pragma once
 
 #define ROCKSDB_MAJOR 4
-#define ROCKSDB_MINOR 5
+#define ROCKSDB_MINOR 6
 #define ROCKSDB_PATCH 0
 
 // Do not use these. We made the mistake of declaring macros starting with