MDEV-5477 sphinxSE GROUP BY on multiple attributes

Translate "multi:" to SPH_GROUPBY_MULTIPLE.
SPH_GROUPBY_ATTRPAIR is still not supported.

storage/sphinx/ha_sphinx.cc

@@ -216,7 +216,9 @@ enum ESphGroupBy
 	SPH_GROUPBY_WEEK	= 1,	///< group by week
 	SPH_GROUPBY_MONTH	= 2,	///< group by month
 	SPH_GROUPBY_YEAR	= 3,	///< group by year
-	SPH_GROUPBY_ATTR	= 4		///< group by attribute value
+	SPH_GROUPBY_ATTR	= 4,	///< group by attribute value
+	SPH_GROUPBY_ATTRPAIR	= 5,	///< group by sequential attrs pair (rendered redundant by 64bit attrs support; removed)
+	SPH_GROUPBY_MULTIPLE	= 6 	///< group by on multiple attribute values
 };
 
 /// known attribute types
@@ -1555,6 +1557,7 @@ bool CSphSEQuery::ParseField ( char * sField )
 			{ "month:",	SPH_GROUPBY_MONTH },
 			{ "year:",	SPH_GROUPBY_YEAR },
 			{ "attr:",	SPH_GROUPBY_ATTR },
+			{ "multi:",     SPH_GROUPBY_MULTIPLE }
 		};
 
 		int i;