I figured it out by looking at the "config.log". Every time it had an error, I would need to download a package with a library or function which got me a little further each time. In V5 the gcc package through unMenu installed: gcc, make, binutils, glibc, and kernel-headers. That was the difference between V5 and V6 ( I am not running unMENU on V6 yet).
I ended up with these packages in my /boot/extra folder:
binutils-2.23.52.0.1-x86_64-2.txz
gcc-4.8.2-x86_64-1.txz
gcc-g++-4.8.2-x86_64-1.txz
git-1.8.4-x86_64-1.txz
glibc-2.17-x86_64-7.txz
kernel-headers-3.10.17-x86-3.txz
libmpc-0.8.2-x86_64-2.txz
make-3.82-x86_64-4.txz
The packages were downloaded from: http://mirrors.slackware.com/slackware/slackware64-14.1/slackware64/
Now I can compile MediaInfo from source and use it in my YAMJ scans.