Added an API in rocksdb for checking for "invalid argument" and "not supported" for leveldb::Status

Summary: a function added to status.h to check whether Status::code is InvalidArgument and similarly for NotSupported state

Test Plan: visual inspection

Reviewers: heyongqiang, dhruba

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D7989

include/leveldb/status.h

@@ -57,6 +57,12 @@ class Status {
   // Returns true iff the status indicates a Corruption error.
   bool IsCorruption() const { return code() == kCorruption; }
 
+  // Returns true iff the status indicates a NotSupported error.
+  bool IsNotSupported() const { return code() == kNotSupported; }
+
+  // Returns true iff the status indicates an InvalidArgument error.
+  bool IsInvalidArgument() const { return code() == kInvalidArgument; }
+
   // Returns true iff the status indicates an IOError.
   bool IsIOError() const { return code() == kIOError; }