Fix fabs warning in gd_interpolation.c

Matches upstream code.

Author: nikic

ext/gd/libgd/gd_interpolation.c

@@ -2398,8 +2398,8 @@ int gdTransformAffineCopy(gdImagePtr dst,
 
 	gdImageGetClip(dst, &c1x, &c1y, &c2x, &c2y);
 
-	end_x = bbox.width  + (int) fabs(bbox.x);
-	end_y = bbox.height + (int) fabs(bbox.y);
+	end_x = bbox.width  + abs(bbox.x);
+	end_y = bbox.height + abs(bbox.y);
 
 	/* Get inverse affine to let us work with destination -> source */
 	gdAffineInvert(inv, affine);