glib-2.0: add HashTable.get_keys_as_array
glib-2.0: add HashTable.get_keys_as_array

flobrosch/vala-fixes,rvu95/vala,flobrosch/vala-fixes,frida/vala,spidermonkdust/vala,frida/vala,GNOME/vala,GNOME/vala,rvu95/vala,spidermonkdust/vala,frida/vala,GNOME/vala,frida/vala,spidermonkdust/vala,frida/vala,rvu95/vala,GNOME/vala,flobrosch/vala-fixes