[indic] Improve base re-finding

No test numbers change.

src/hb-ot-shape-complex-indic.cc

@@ -1353,11 +1353,10 @@ final_reordering_syllable (const hb_ot_shape_plan_t *plan,
       break;
     }
   if (base == end && start < base &&
-      info[base - 1].indic_category() != OT_ZWJ)
+      is_one_of (info[base - 1], FLAG (OT_ZWJ)))
     base--;
   while (start < base &&
-	 (info[base].indic_category() == OT_H ||
-	  info[base].indic_category() == OT_N))
+	 is_one_of (info[base], (FLAG (OT_N) | HALANT_OR_COENG_FLAGS)))
     base--;