vimeo: do not trust gcrypt to zero-terminate a digest
vimeo: do not trust gcrypt to zero-terminate a digest

For some unknown reason, gcrypt does not always zero-terminate the digest it
returns. This means some requests failed because the oauth signature was wrong.

With this commit, #639965[1] should be fixed.

[1] https://bugzilla.gnome.org/show_bug.cgi?id=639965

grilofw/grilo-plugins,vrutkovs/grilo-plugins,MikePetullo/grilo-plugins,kyoushuu/grilo-plugins,GNOME/grilo-plugins,MathieuDuponchelle/grilo-plugins,MathieuDuponchelle/grilo-plugins,kyoushuu/grilo-plugins,jasuarez/grilo-plugins,vrutkovs/grilo-plugins,MathieuDuponchelle/grilo-plugins,GNOME/grilo-plugins,kyoushuu/grilo-plugins,MikePetullo/grilo-plugins,grilofw/grilo-plugins,vrutkovs/grilo-plugins,MathieuDuponchelle/grilo-plugins,vrutkovs/grilo-plugins,MikePetullo/grilo-plugins,jasuarez/grilo-plugins