recentinfo.hg: Fix Visual Studio build

Hi,

From the commit message:

Nowadays, gtk has its visibility macros generated and make use of __declspec(dllimport) in addition to __declspec(dllexport), so we must decorate the void gtk_recent_info_unref(GtkRecentInfo* info); prototype with GDK_AVAILABLE_IN_ALL, so that we don't end up with warnings and errors when we include the GDK headers when building this code, as this prototype can exist before the GDK/GTK headers get included.

The cost is that we must include gdk/version/gdk-visibility.h here so that macro gets defined as appropriate.

With blessings, thank you!