Summary:
Adding -W and -Wextra to CXXFLAGS provoked this failure:

	  table/table_test.cc:1854:56: error: missing initializer for member ‘rocksdb::TestArgs::format_version’ [-Werror=missing-field-initializers]
	     TestArgs args = { DB_TEST, false, 16, kNoCompression };
	                                                          ^

Add the missing, 5th value (format_version).

Test Plan:
  Run "make EXTRA_CXXFLAGS='-W -Wextra'" and see fewer errors.

Reviewers: ljin, sdong, igor.sugak, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D33765