Summary:
The batched version of MultiGet() is not available in RocksDB's C API.
This PR implements rocksdb_batched_multi_get_cf which is a C wrapper function
that invokes the batched version of MultiGet() which takes one single column family.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9952
Test Plan: Added a new test case under "columnfamilies" test case in c_test.cc
Reviewed By: riversand963
Differential Revision: D36302888
Pulled By: ajkr
fbshipit-source-id: fa134c4a1c8e7d72dd4ae8649a74e3797b5cf4e6
bcb1287235