package/libfribidi: remove optional dependency to libglib

package/libfribidi: remove optional dependency to libglib

Fixes vdr compile error:
http://autobuild.buildroot.net/results/725/7252decffe29e19051eed0554786651aee216573/

Instead of fixing fribidi.pc or adding optional CFLAGS to the vdr
package we remove the optional libglib dependency because it does not
contain "any thing substantial" as pointed out in an pull request sent
upstream: https://github.com/behdad/fribidi/pull/14

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>