package/vlc: fix linking with tremor

Patch 0004 is not enough anymore to fix linking with tremor (provides
libvorbisidec) so we provide the proper content for VORBIS_LIBS.

Fixes
http://autobuild.buildroot.net/results/15a/15a3c5b90de6c67db9887e3db67b3568f6d18e3a/
http://autobuild.buildroot.net/results/946/946f397bb81ce2c69384fa1e378c40600fd405b6/
http://autobuild.buildroot.net/results/f5d/f5d9f3df78626178274c1be878a2ae0b90394885/
http://autobuild.buildroot.net/results/2e5/2e5dc746a59798a56d3127aadc88593fc584c010/



Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>