ui: increase min required GTK3 version to 3.14.0

Per supported platforms doc[1], the various min GTK3 on relevant distros is:

  RHEL-7.0: 3.8.8
  RHEL-7.2: 3.14.13
  RHEL-7.4: 3.22.10
  RHEL-7.5: 3.22.26
  Debian (Stretch): 3.22.11
  Debian (Jessie): 3.14.5
  OpenBSD (Ports): 3.22.30
  FreeBSD (Ports): 3.22.29
  OpenSUSE Leap 15: 3.22.30
  SLE12-SP2: Unknown
  Ubuntu (Xenial): 3.18.9
  macOS (Homebrew): 3.22.30

This suggests that a minimum GTK3 of 3.14.0 is a reasonable target,
as users are unlikely to be stuck on RHEL-7.0/7.1 still

[1] https://qemu.weilnetz.de/doc/qemu-doc.html#Supported-build-platformsSigned-off-by: NDaniel P. Berrangé <berrange@redhat.com>
Message-id: 20180822131554.3398-3-berrange@redhat.com
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

configure

@@ -2644,7 +2644,7 @@ fi
 if test "$gtk" != "no"; then
     gtkpackage="gtk+-3.0"
     gtkx11package="gtk+-x11-3.0"
-    gtkversion="3.0.0"
+    gtkversion="3.14.0"
     if $pkg_config --exists "$gtkpackage >= $gtkversion"; then
         gtk_cflags=$($pkg_config --cflags $gtkpackage)
         gtk_libs=$($pkg_config --libs $gtkpackage)

ui/gtk.c

@@ -998,7 +998,6 @@ static gboolean gd_scroll_event(GtkWidget *widget, GdkEventScroll *scroll,
         btn = INPUT_BUTTON_WHEEL_UP;
     } else if (scroll->direction == GDK_SCROLL_DOWN) {
         btn = INPUT_BUTTON_WHEEL_DOWN;
-#if GTK_CHECK_VERSION(3, 4, 0)
     } else if (scroll->direction == GDK_SCROLL_SMOOTH) {
         gdouble delta_x, delta_y;
         if (!gdk_event_get_scroll_deltas((GdkEvent *)scroll,
@@ -1010,7 +1009,6 @@ static gboolean gd_scroll_event(GtkWidget *widget, GdkEventScroll *scroll,
         } else {
             btn = INPUT_BUTTON_WHEEL_UP;
         }
-#endif
     } else {
         return TRUE;
     }
@@ -1672,11 +1670,9 @@ static GSList *gd_vc_menu_init(GtkDisplayState *s, VirtualConsole *vc,
     gtk_accel_group_connect(s->accel_group, GDK_KEY_1 + idx,
             HOTKEY_MODIFIERS, 0,
             g_cclosure_new_swap(G_CALLBACK(gd_accel_switch_vc), vc, NULL));
-#if GTK_CHECK_VERSION(3, 8, 0)
     gtk_accel_label_set_accel(
             GTK_ACCEL_LABEL(gtk_bin_get_child(GTK_BIN(vc->menu_item))),
             GDK_KEY_1 + idx, HOTKEY_MODIFIERS);
-#endif
 
     g_signal_connect(vc->menu_item, "activate",
                      G_CALLBACK(gd_menu_switch_vc), s);
@@ -2175,11 +2171,9 @@ static GtkWidget *gd_create_menu_view(GtkDisplayState *s)
                                    TRUE);
     gtk_accel_group_connect(s->accel_group, GDK_KEY_m, HOTKEY_MODIFIERS, 0,
             g_cclosure_new_swap(G_CALLBACK(gd_accel_show_menubar), s, NULL));
-#if GTK_CHECK_VERSION(3, 8, 0)
     gtk_accel_label_set_accel(
             GTK_ACCEL_LABEL(gtk_bin_get_child(GTK_BIN(s->show_menubar_item))),
             GDK_KEY_m, HOTKEY_MODIFIERS);
-#endif
     gtk_menu_shell_append(GTK_MENU_SHELL(view_menu), s->show_menubar_item);
 
     return view_menu;
@@ -2229,11 +2223,7 @@ static void gtk_display_init(DisplayState *ds, DisplayOptions *opts)
     s->opts = opts;
 
     s->window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
-#if GTK_CHECK_VERSION(3, 2, 0)
     s->vbox = gtk_box_new(GTK_ORIENTATION_VERTICAL, 0);
-#else
-    s->vbox = gtk_vbox_new(FALSE, 0);
-#endif
     s->notebook = gtk_notebook_new();
     s->menu_bar = gtk_menu_bar_new();