Add Filter to Nav Menu Support Themes Text

[wpsmith]

Frameworks could use a filter here to customize the message: _n('Your theme supports %s menu. Select which menu you would like to use.', 'Your theme supports %s menus. Select which menu appears in each location.', $num_locations ). For example, it may be the child theme that doesn't support the menus. Also, if none are supported (say via add_theme_support), then when it's zero, it says: "Your theme supports 0 menus. Select which menu appears in each location." (which doesn't make much sense). So adding a filter can enable theme developers to further customize.

An example use case:
add_filter( 'nav_menu_theme_support_text' , 'wps_nav_menu_theme_support_text' );
function wps_nav_menu_theme_support_text ( $num_locations ) {

if ( $num_locations == 0 )

$text = 'Your child theme does not support custom menus.';

else

$text = _n('Your theme supports %s menu. Select which menu you would like to use.', 'Your theme supports %s menus. Select which menu appears in each location.', $num_locations );

return $text;

}