patch 8.0.1135: W_WINCOL() is always the same

Problem:    W_WINCOL() is always the same.
Solution:   Expand the macro.
diff --git a/src/gui_gtk.c b/src/gui_gtk.c
index af8fcae..b321da0 100644
--- a/src/gui_gtk.c
+++ b/src/gui_gtk.c
@@ -1954,7 +1954,7 @@
 # endif
     {
 	/* Find the cursor position in the current window */
-	*x += FILL_X(W_WINCOL(curwin) + curwin->w_wcol + 1) + 1;
+	*x += FILL_X(curwin->w_wincol + curwin->w_wcol + 1) + 1;
 	*y += FILL_Y(W_WINROW(curwin) + curwin->w_wrow + 1) + 1;
     }
 }