A few compiling issues

I had a few issues compiling, and these commits fix them. I'm not sure if perhaps there was an issue on my end with GEANT versions w.r.t. -Werror (I used 4.9.6.p03), so maybe someone can confirm.
That should be fine, as library version changes are rare (and would probably fail to link anyway). Can add to the docs a warning to always `scons -c` when updating libraries.