Add C/C++ settings from last time I played around with emacs

These will need quite a bit of tweaking still, I think, but it's enough
to get started.
Don't remap window navigation in evil (I'm happy enough with C-w + dir)
Manually fix C-u, since evil-want-C-u-scroll doesn't seem to work
Hide the toolbar
Wrap elisp-slime-nav in usepackage
Don't backup files (Git generally gives me what I need here)
Set line numbers on, globally
Visible whitespace
Hide ^M from mixed-newline files

Not TOTALLY convinced this is a good idea, but so long as I'm working
with Visual Studio types it's going to keep coming up, and the ^Ms are
really annoying.
Make scrolling nicer
Attempt at stopping emacs from changing directory all the time

I want to choose a directory and stay in it, and open all files relative
to that directory, but emacs works on a "relative to the current buffer"
basis.  This attempts to fix that by modifying functions like
find-file-noselect-1 and set-visited-file-name to restore the directory
after operation.  Sometimes directory changes still sneak in, though --
I think this is just a case of hunting down any other functions which do
it and turning it off.