xbmc-pvr-addons: update to xbmc-pvr-addons-18c52bb

Signed-off-by: Stephan Raue <stephan@openelec.tv>
tools/mkpkg: add script to get and pack 'xbmc-pvr-addons' for gotham

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