Add, export, and test multiple functions, structs and constants
Add `cl-hexdump.lisp` to autogenerate hexdumps from assets

 Remove manually generated asset hexdumps. Use instead
 simple Common Lisp program to iterate asset directory
 and generate a Lisp hexdump for each asset. Update
 this step as a prerquisite for Makefile's `test`
Add, export, and test more functions, change project structure
Add, export and test some sound and music related things

 * Add foreign functions for loading, releasing
   and playing SDL2 chunks and music.
 * Add `with-*` helper macros for working with sound.
 * Add `audio` class, functions, and method for playing
   it. Constructor takes care of all the foreign allocation and
   setup, and destructor releases all foreign data.
 * Disable FreeBSD and OpenBSD CI runner for now.
   For some reason, they don't work on remote headless
   server as well as on local headless VM.
Do some changes for CI runners
Use Xvfb to run unit tests without display on CI
Add, export, and test few functions
Add, export, and test macros and foreign functions, add test asset
WIP Add mixer
Add, export, and test more constants
Make names shorter, add package nickname, etc.

 * Make names shorter, for example `init` instead
   of `sdl-init`. If using package nickname `sdl`,
   this is then written `sdl:init`.

 * Add, export, and test one new constant.

 * Add unit test runner for OpenBSD.
Make unit test runner for ECL silent, and for CLISP more silent
Fix FreeBSD 13.x unit test runner
Add unit test runner for FreeBSD 13.x
Fix shellcheck errors in unit test script, load SDL2 in macOS
Fix Debian unit test runner by enabling Quicklisp for CLISP
Modify Debian GNU/Linux unit test runner
Fix unit test runner for Debian GNU/Linux

 * Make Quicklisp available in ECL
Fix and update unit tets runner for Debian GNU/Linux
Modify unit test runner script