Scanfill: skip checks for loose edges when they can't occur

Only editmesh needs this, text, curves, masks - can all skip this check

source/blender/blenlib/BLI_scanfill.h

@@ -98,7 +98,10 @@ enum {
 
 	/* note: This flag removes checks for overlapping polygons.
 	 * when this flag is set, we'll never get back more faces then (totvert - 2) */
-	BLI_SCANFILL_CALC_HOLES            = (1 << 2)
+	BLI_SCANFILL_CALC_HOLES            = (1 << 2),
+
+	/* checks valid edge users - can skip for simple loops */
+	BLI_SCANFILL_CALC_LOOSE            = (1 << 3),
 };
 void BLI_scanfill_begin(ScanFillContext *sf_ctx);
 unsigned int BLI_scanfill_calc(ScanFillContext *sf_ctx, const int flag);