WIP: Show error messages from failed dlopen

[tkelman]

This is an attempt to fix #123 - unfortunately I'm not getting any useful error message for the WinRPM issue from https://github.com/JuliaLang/ZMQ.jl/issues/69, and strangely the warning is getting repeated twice, once before and once after INFO: Nothing to do.

This might help with issues like we've seen with libgfortran though, I'll have to test on Linux.