First-draft Debian packaging implementation.

First-draft Debian packaging implementation.

I've split up the installed files into three packages. Following the
upstream names of the binaries, the package 'chroma' contains the
graphical SDL version of the game, and 'chroma-curses' contains the
terminal-based version. They're in separate packages so that each one
can avoid the library dependencies of the other.

The shared data between the two (mostly level designs) lives in a
third package 'chroma-data'. But not all the stuff upstream installs
in /usr/share/chroma goes in there: the SVG graphics used only by the
SDL binary can live in the 'chroma' package.

Upstream's makefile installs binaries in /usr/bin; per Debian policy,
the packaging moves them to /usr/games.

An icon for the .desktop file is constructed from one of the SVGs in
the upstream tarball, but because that SVG contains two images side by
side, I had to provide a small Python script that extracts just one of
them (and then passes it to Inkscape to render into a PNG).