Make members of class ha_rocksdb respect the code conventions

Summary:
  Have class ha_rocksdb member names start with m_
  Introduce open table map class
  Add new function my_hash_const_element(), the const equivalent of my_hash_element()
  Rename ROCKSDB_SHARE into Rdb_table_handler

Test Plan:
  myqlbuild.sh --clean
  mysqltest.sh
  mysqltest.sh --testset=RocksDB
  myqlbuild.sh --clean --release

Reviewers: jkedgar

Reviewed By: jkedgar

Subscribers: webscalesql-eng

Projects: #webscalesql

Differential Revision: https://reviews.facebook.net/D58305

include/hash.h

@@ -89,6 +89,7 @@ my_bool _my_hash_init(HASH *hash, uint growth_size, CHARSET_INFO *charset,
 void my_hash_free(HASH *tree);
 void my_hash_reset(HASH *hash);
 uchar *my_hash_element(HASH *hash, ulong idx);
+const uchar *my_hash_const_element(const HASH *hash, ulong idx);
 uchar *my_hash_search(const HASH *info, const uchar *key, size_t length);
 uchar *my_hash_search_using_hash_value(const HASH *info,
                                        my_hash_value_type hash_value,

mysys/hash.c

@@ -717,6 +717,14 @@ uchar *my_hash_element(HASH *hash, ulong idx)
 }
 
 
+const uchar *my_hash_const_element(const HASH *hash, ulong idx)
+{
+  if (idx < hash->records)
+    return dynamic_element(&hash->array,idx,const HASH_LINK*)->data;
+  return 0;
+}
+
+
 /*
   Replace old row with new row.  This should only be used when key
   isn't changed

storage/rocksdb/README

@@ -25,6 +25,9 @@ Several refinements:
   7. Given the 80 character per line limit, we'll not always use full English
      words in names, when a well known or easily recognizable abbreviation
      exists (like "tx" for "transaction" or "param" for "parameter" etc).
+  8. When needing to disambiguate, we use different suffixes for that, like
+     "_arg" for a function argument/parameter, "_arr" for a C style array, and
+     "_vect" for a std::vector etc.
 
 == Running Tests ==
 To run tests from rocksdb, rocksd_rpl or rocksdb_sys_vars packages, use the following parameters: