Renamed 'hybrid_compaction' tp be "Universal Compaction'.

Summary:
All the universal compaction parameters are encapsulated in
a new file universal_compaction.h

Test Plan:
make check

include/leveldb/options.h

@@ -12,6 +12,7 @@
 #include <stdint.h>
 #include "leveldb/slice.h"
 #include "leveldb/statistics.h"
+#include "leveldb/universal_compaction.h"
 
 namespace leveldb {
 
@@ -39,6 +40,11 @@ enum CompressionType {
   kBZip2Compression = 0x3
 };
 
+enum CompactionStyle {
+  kCompactionStyleLevel       = 0x0, // level based compaction style
+  kCompactionStyleUniversal   = 0x1  // Universal compaction style
+};
+
 // Compression options for different compression algorithms like Zlib
 struct CompressionOptions {
   int window_bits;
@@ -132,7 +138,7 @@ struct Options {
   int max_write_buffer_number;
 
   // The minimum number of write buffers that will be merged together
-  // before writing to storage.  If set to 1, then 
+  // before writing to storage.  If set to 1, then
   // all write buffers are fushed to L0 as individual files and this increases
   // read amplification because a get request has to check in all of these
   // files. Also, an in-memory merge may result in writing lesser
@@ -476,17 +482,12 @@ struct Options {
   // Default: 0
   uint64_t bytes_per_sync;
 
-  // Hybrid Mode. There is only a single level and files in L0 are
+  // The compaction style
   // compacted back into L0. Default: false
-  bool hybrid_mode;
+  CompactionStyle compaction_style;
 
-  // Percentage flexibilty while comparing file size. If the candidate file(s)
-  // size is 1% smaller than the next file's size, then include next file into
-  // this candidate set. // Default: 1
-  int hybrid_size_ratio;
-
-  // The minimum number of files in a single compaction run. Default: 2
-  int hybrid_min_numfiles_in_single_compaction;
+  // The options needed to support Universal Style compactions
+  CompactionOptionsUniversal compaction_options_universal;
 };
 
 // Options that control read operations

include/leveldb/universal_compaction.h

@@ -0,0 +1,57 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_ROCKSDB_UNIVERSAL_COMPACTION_OPTIONS_H
+#define STORAGE_ROCKSDB_UNIVERSAL_COMPACTION_OPTIONS_H
+
+#include <stddef.h>
+#include <string>
+#include <memory>
+#include <vector>
+#include <stdint.h>
+#include <climits>
+#include "leveldb/slice.h"
+#include "leveldb/statistics.h"
+
+namespace leveldb {
+
+//
+// Algorithm used to make a compaction request stop picking new files
+// into a single compaction run
+//
+enum CompactionStopStyle {
+  kCompactionStopStyleSimilarSize, // pick files of similar size
+  kCompactionStopStyleTotalSize    // total size of picked files > next file
+};
+
+class CompactionOptionsUniversal {
+ public:
+
+  // Percentage flexibilty while comparing file size. If the candidate file(s)
+  // size is 1% smaller than the next file's size, then include next file into
+  // this candidate set. // Default: 1
+  unsigned int size_ratio;
+
+  // The minimum number of files in a single compaction run. Default: 2
+  unsigned int min_merge_width;
+
+  // The maximum number of files in a single compaction run. Default: INT_MAX
+  unsigned int max_merge_width;
+
+  // The algorithm used to stop picking files into a single compaction run
+  // Default: kCompactionStopStyleTotalSize
+  CompactionStopStyle stop_style;
+
+  // Default set of parameters
+  CompactionOptionsUniversal() :
+    size_ratio(1),
+    min_merge_width(2),
+    max_merge_width(UINT_MAX),
+    stop_style(kCompactionStopStyleTotalSize) {
+  }
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_ROCKSDB_UNIVERSAL_COMPACTION_OPTIONS_H