Include <array> in table/plain_table_key_coding.h

Summary: <array> is not included in table/plain_table_key_coding.h. It may be the cause of one CLANG build failure.

Test Plan: Build it

Reviewers: yhchiang, rven, IslamAbdelRahman

Reviewed By: IslamAbdelRahman

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D52725

table/plain_table_key_coding.h

@@ -6,6 +6,7 @@
 #pragma once
 #ifndef ROCKSDB_LITE
 
+#include <array>
 #include "rocksdb/slice.h"
 #include "db/dbformat.h"
 #include "table/plain_table_reader.h"