Fix a typo and update HISTORY.md for NewCompactOnDeletionCollectorFactory().

Summary: Fix a typo and update HISTORY.md for NewCompactOnDeletionCollectorFactory().

Test Plan: no code change.

Reviewers: igor, anthony, IslamAbdelRahman, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D43521

HISTORY.md

@@ -5,6 +5,7 @@
 ### New Features
 * Add DBOptions::skip_stats_update_on_db_open.  When it is on, DB::Open() will run faster as it skips the random reads required for loading necessary stats from SST files to optimize compaction.
 * RollbackToSavePoint() in WriteBatch/WriteBatchWithIndex
+* Add NewCompactOnDeletionCollectorFactory() in utilities/table_properties_collectors, which allows rocksdb to mark a SST file as need-compaction when it observes at least D deletion entries in any N consecutive entries in that SST file.  Note that this feature depends on an experimental NeedCompact() API which result will not persist after DB restart.
 
 ### Public API Changes
 * Deprecated WriteOptions::timeout_hint_us. We no longer support write timeout. If you really need this option, talk to us and we might consider returning it.

include/rocksdb/utilities/table_properties_collectors.h

@@ -16,7 +16,7 @@ namespace rocksdb {
 // entries in any "N" consecutive entires.
 //
 // @param sliding_window_size "N". Note that this number will be
-//     round up to the smallest multilpe of 128 that is no less
+//     round up to the smallest multiple of 128 that is no less
 //     than the specified size.
 // @param deletion_trigger "D".  Note that even when "N" is changed,
 //     the specified number for "D" will not be changed.