Clean up layering of storage/leveldb/...

With these changes, this package should be properly cleaned up and not require
any further changes.

db/snapshot.h

@@ -5,6 +5,7 @@
 #ifndef STORAGE_LEVELDB_DB_SNAPSHOT_H_
 #define STORAGE_LEVELDB_DB_SNAPSHOT_H_
 
+#include "db/dbformat.h"
 #include "leveldb/db.h"
 
 namespace leveldb {

db/write_batch_internal.h

@@ -5,6 +5,7 @@
 #ifndef STORAGE_LEVELDB_DB_WRITE_BATCH_INTERNAL_H_
 #define STORAGE_LEVELDB_DB_WRITE_BATCH_INTERNAL_H_
 
+#include "db/dbformat.h"
 #include "leveldb/write_batch.h"
 
 namespace leveldb {

table/iterator_wrapper.h

@@ -5,6 +5,9 @@
 #ifndef STORAGE_LEVELDB_TABLE_ITERATOR_WRAPPER_H_
 #define STORAGE_LEVELDB_TABLE_ITERATOR_WRAPPER_H_
 
+#include "leveldb/iterator.h"
+#include "leveldb/slice.h"
+
 namespace leveldb {
 
 // A internal wrapper class with an interface similar to Iterator that