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.
This is doable but scons does not have internal support for ```-isystem```. The only negative side effect of doing this is scons will not check the ```-isystem``` directories for updates to header files.