As stated in bug 112367, if mkvtoolnix is compiled with =lzo-2* installed and no lzo1, then lzo is support is quietly dropped. Solution part 1 is to make the DEPEND in mkvtoolnix*.ebuild to =dev-libs/lzo-1* Solution part 2 is to use the attached patches to create a lzo2 revision.
Created attachment 72796 [details, diff] mkvtoolnix-1.6.0.ebuild-lzo2.patch Patch against current ebuild to include lzo2 support.
Created attachment 72797 [details, diff] files/mkvtoolnix-1.6.0-lzo2.patch configure patch to detect lzo2
I'm going to try a little different way, I have a patch, have to test it tho.
Committed, and sent upstream.