Syntax files for vim

To use these files just do something like:

mkdir -p ~/.vim ~/.vim/ftdetect ~/.vim/syntax
cp bonus/vim/ftdetect/* ~/.vim/ftdetect/
cp bonus/vim/syntax/* ~/.vim/syntax/

For example, opening the hello.i example program produces something like:

     https://uilebheist.srht.site/img/syntax.jpg

(assuming your terminal is set to dark background; for light background it
will look different).

