gettext: update to gettext-0.19.4

Signed-off-by: Stephan Raue <stephan@openelec.tv>
libpng: update to libpng-1.6.16

Signed-off-by: Stephan Raue <stephan@openelec.tv>
kodi: update to kodi-14-ad747d9, this fixes #3718

Signed-off-by: Stephan Raue <stephan@openelec.tv>