patch 8.0.1136: W_WIDTH() is always the same

Problem:    W_WIDTH() is always the same.
Solution:   Expand the macro.
diff --git a/src/gui.c b/src/gui.c
index 4f9c63f..a17c571 100644
--- a/src/gui.c
+++ b/src/gui.c
@@ -4564,14 +4564,14 @@
 	return;
     }
 
-    size = W_WIDTH(curwin);
+    size = curwin->w_width;
     if (curwin->w_p_wrap)
     {
 	value = 0;
 #ifdef SCROLL_PAST_END
 	max = 0;
 #else
-	max = W_WIDTH(curwin) - 1;
+	max = curwin->w_width - 1;
 #endif
     }
     else
@@ -4591,7 +4591,7 @@
 #endif
 
 #ifndef SCROLL_PAST_END
-	max += W_WIDTH(curwin) - 1;
+	max += curwin->w_width - 1;
 #endif
 	/* The line number isn't scrolled, thus there is less space when
 	 * 'number' or 'relativenumber' is set (also for 'foldcolumn'). */