Port the whole Jou compiler to Jou

[Akuli]

I ported the whole Jou compiler to Jou. The self-hosted compiler can now compile anything that the original Jou compiler can.

The self-hosted compiler can compile itself. In the below command, I called the result compiler2.

$ ./self_hosted_compiler -o compiler2 --linker-flags "-L/usr/lib/llvm-14/lib -lLLVM-14" self_hosted/main.jou 
$ ./compiler2 examples/hello.jou 
Hello World

Of course, the self-hosted compiler compiled with the self-hosted compiler can also compile the self-hosted compiler. I called it compiler3.

$ ./compiler2 -o compiler3 --linker-flags "-L/usr/lib/llvm-14/lib -lLLVM-14" self_hosted/main.jou 
$ ./compiler3 examples/hello.jou 
Hello World

This is something I have wanted to achieve for quite some time.

Caveats:

• Code is messy. I ported most of it by taking C code and modifying it until it works.
• It leaks memory. Some memory freeing code is commented out.
• It lacks the simplify_cfg compilation step. Apparently, the only real consequence of this is that you won't get a compiler warning if you forget a return statement in a function.

See also other checkboxes in #116.

[Akuli]

The diff of this pull request looks big because I moved the old self-hosted compiler to new folder self_hosted_old.

That said, the new self-hosted compiler is quite different from the old one, so in that sense I did a lot of work: