g_bytes_icon_new is only in glib >= 2.38

Change-Id: I57f2d016eb6d35d2bc9be090444be1190d68d11d
diff --git a/vcl/unx/gtk/gtksalmenu.cxx b/vcl/unx/gtk/gtksalmenu.cxx
index 081ca54..a08917a 100644
--- a/vcl/unx/gtk/gtksalmenu.cxx
+++ b/vcl/unx/gtk/gtksalmenu.cxx
@@ -859,6 +859,7 @@ namespace

void GtkSalMenu::NativeSetItemIcon( unsigned nSection, unsigned nItemPos, const Image& rImage )
{
#if GLIB_CHECK_VERSION(2,38,0)
    SolarMutexGuard aGuard;

    SvMemoryStream* pMemStm = new SvMemoryStream;
@@ -874,6 +875,11 @@ void GtkSalMenu::NativeSetItemIcon( unsigned nSection, unsigned nItemPos, const 
    g_lo_menu_set_icon_to_item_in_section( G_LO_MENU( mpMenuModel ), nSection, nItemPos, pIcon );
    g_object_unref(pIcon);
    g_bytes_unref(pBytes);
#else
    (void)nSection;
    (void)nItemPos;
    (void)rImage;
#endif
}

void GtkSalMenu::NativeSetAccelerator( unsigned nSection, unsigned nItemPos, const vcl::KeyCode& rKeyCode, const OUString& rKeyName )