linux: update to linux-3.7.8

Signed-off-by: Stephan Raue <stephan@openelec.tv>
libpng: update to libpng-1.5.14

Signed-off-by: Stephan Raue <stephan@openelec.tv>
pkg-config: update to pkg-config-0.28

Signed-off-by: Stephan Raue <stephan@openelec.tv>
libmicrohttpd: update to libmicrohttpd-0.9.25

Signed-off-by: Stephan Raue <stephan@openelec.tv>
xkeyboard-config: update to xkeyboard-config-2.8

Signed-off-by: Stephan Raue <stephan@openelec.tv>
xf86-video-intel: update to xf86-video-intel-2.21.0

Signed-off-by: Stephan Raue <stephan@openelec.tv>
libvdpau: update to libvdpau-0.6

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