patch 8.2.2043: GTK3: white border around text stands out

Problem:    GTK3: white border around text stands out.
Solution:   Use current theme color. (closes #7357, issue #349)

src/gui_gtk_x11.c

@@ -4039,10 +4039,10 @@ gui_mch_new_colors(void)
 
 #if GTK_CHECK_VERSION(3,22,2)
 	GtkStyleContext * const context
-	    = gtk_widget_get_style_context(gui.drawarea);
+	    = gtk_widget_get_style_context(gui.mainwin);
 	GtkCssProvider * const provider = gtk_css_provider_new();
 	gchar * const css = g_strdup_printf(
-		"widget#vim-gui-drawarea {\n"
+		"widget#vim-gui-drawarea, #vim-main-window {\n"
 		"  background-color: #%.2lx%.2lx%.2lx;\n"
 		"}\n",
 		 (gui.back_pixel >> 16) & 0xff,

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2043,
 /**/
     2042,
 /**/